I was going to have a more thorough delve into the data (including average speeds) next week when the holidays are over.
Had a brief look at the data (the "Full Data" sheet here:
https://docs.google.com/spreadsheets/d/1e6hVMqFKwaIvcj-Mx8GNRs1UZl5QiYmbg4LZjMMLYwg/edit#gid=0 )
If we assume that Steve will need 220mpd+ over the next ~210 days then he either needs to get faster, spend longer in the saddle each day, or a combination of both.
His two original schedules differed by the expected average speeds. The time spent each day in the saddle was the same for each month.
The next thing I did was to think about how many hours I’d expect to spend riding, not including stops, on a typical day for whichever given month. For example, I thought that spending 12-14 hours would be about right for a typical January day, on a daily basis. Whereas in June, riding for 16-18 hours would be about right. I based the figures on my years of experience of all year round long distance cycling.
(I strongly doubt that Steve can ride 18 hours a day, day in day out for more than 2 months. With a couple of hours off the bike for eating, washing, toilet, etc that's only 4 hours sleep a day. He might have been able to maintain that for a couple of weeks on some previous long ride [Grand Triangle/etc] but that doesn't mean he can do it for 60+ days).
All following calculations start from Jan 1st 2016, so his mileage to that point is 27827.7 miles and he needs the rest (based on a 76000 mile record from Kurt) over the remaining 219 days (219.96mpd).
The historical data shows he was able to regularly do 13.5 hours a day moving time as he has managed this consistently when not injured, recovering or ill. He'll only have a good chance at the record from the restart if he avoids illness and injury! But he never had a 7 day average of more than 14.5 hours. Would this have been different without the injury or illness, we don't know. But basing a schedule on the expectation of being able to move up to 16h moving time a day is certainly risky (but we'll have a go). It just may not possible with that level of accumulated fatigue. It's one thing Steve can't plan as he's never tried to ride that much consistently with this level of accumulated fatigue.
His current mean ride speed is 14.65mph (from the restart, it was 14.54mph for the original attempt) but these include some slower days due to injury/etc. The interquartile mean (i.e. the average after throwing away the shortest quarter and longest quarter of results) for the second attempt is 14.91mph (see the "Statistics" sheet on the google docs link above for more info on this).
So, for scenario #1 (he gets faster) let's assume he can peak at 14 hours a day even in the summer. I'll take Jan/Feb to be 13h/day, Mar 13.5h/day and Apr/May/Jun/Jul/Aug at 14h/day.
At 14.65mph this works out at 190.45miles, 197.775miles and 205.1miles and, no great surprise, he's 4361 miles short of 76000.
How fast would he need to get within the constraints of those hourly riding limits and good luck of no illness or off days...
Those riding times add to 2990.5 hours over those 219 days. (76000-27827.7)/2990.5 = 16.11mph
A progressive increase from the current 14.65mph would be bad. January at 14.65mph and Feb at 15.5mph would require the rest of the riding to be done at 16.5mph to beat the expected 76000. If he's going to increase his speed (and not the time he rides) then he needs to magically get faster right now (whether this is drafting, lifts for tailwinds, whatever).
Scenario 2 (he rides for longer each day):-
Steve seems happy currently riding 13 hour days, so lets reset the schedule to:
Jan/Feb: 13h
Mar: 13.5h
Apr: 14h
May: 15h
Jun/Jul: 16h
Aug: 16h (he's only got 6 days in August so we'll increase it from the original plan of 15h).
Note that the later figures are the lower end of his estimates for how long he could do (I'll work it out with the middle and upper ends in a bit).
That works out at a total of 3155.5 hours over the remaining 219 days.
If he rides to this schedule at his current average speed (14.65mph) he misses by (76000-27827.7)-(3155.5*14.65) = 1944.225 miles.
That's close, so how much faster would he have to ride if he rides for longer.
Scenario 3 (he rides faster and for longer...):-
Take those 3155.5 hours of the lower end of the revised schedule...
(76000-27827.7)/3155.5 = 15.26mph
That's an increase of 0.7mph on what he's been doing recently (and the interquartile mean speed for the original attempt was 14.85mph and the restarted attempt 14.91mph, so he's not far off that already).
At the middle of the spectrum we add a further hour each day to get 3374.5 hours. (76000-27827.7)/3374.5 = 14.3mph
At the top end of the spectrum we add another hour each day to get 3593.5 hours. (76000-27827.7)/3593.5 = 13.41mph
But I strongly doubt that Steve (or anyone really) can put in 17 let alone 18 hours a day of riding for 60+ days consistently.
The lower end of the schedule may be possible as it represents 4 months of roughly what he is doing now (and has done for many months in total) followed by 3 and a bit months of longer hours, but it's still an unknown (as Steve has never consistently managed more than 14 hours a day of moving time). 16 hours a day riding time leaves very little time for sleep after eating/ablutions/shower/chores/etc.
The lower version ends up as an average speed of 15.26mph and daily distances of 198.9 (Jan/Feb), 206.55 (Mar), 214.2 (Apr), 229.5 (May), 244.8 (Jun/Jul/Aug).
A slight speed increase is required but I think the key will be to optimising his day to make fitting in the longer rides easier. 1h30m pub lunch stops (like this evening) are going to eat (no pun intended) into his sleep and recovery. Sitting down and resting whilst you wait/eat food is one thing, and some of it is required as you can't just bolt your food down and go straight back out on the bike, but it's not sleep. I haven't looked at Kurt's stopped time data but I assume it's considerably less as Alicia can time the food preparation perfectly for his arrival so he is in complete control of how long he stops for.
Steve relying on commercial food stops is a big risk to this but it might be managable depending on his diet and with good planning. Any extra time (than planned) waiting means lost sleep. Start gaining too much sleep debt and the riding time per day or speed suffers (and, like several have pointed out, shows as a bunch of good long days followed by one or two shorter days with all the advantage of the longer days lost).
Obviously other tactics (lifts to the start of a tailwind, drafting) are possibilities but they come with their own trade-offs and problems[1], but any increase in average speed will help keep the sleep debt in check if time isn't wasted on other things.
Anyway, that's enough, it's made me a lot more positive about the continuation with the restarted attempt
but it all hinges on whether Steve can get that little bit faster and build up to a few more hours riding each day and maintain this almost without fail.
1. Organisation most notably, and taking the pathological case of being driven 300km every day to the start of a tailwind means at least 3 hours a day in a car, which doesn't lend itself well to quality sleep and isn't that productive...picking numbers from my arse: 150km into the wind at 22kph = 6.81h, 150km with the wind at 32kph = 4.68h. The 3 hour car journey would just be saving you 6.81h-4.68h = 2h 8m, so a net loss. You'd need 150km at 22kph to be balanced by 150km at 40kph to earn back the 3 hours it would take to drive back to the start point (assuming 100kph). Unlikely. Kurt benefits from tailwind lifts because he's sleeping in the camper van so he doesn't have his sleep disrupted at the end of the transfer.