A 50 is significantly higher intensity than riding a 24 hour.
My fastest 40km on my Garmin is only about 3 minutes slower than my 25 mile PB and I think that was done during my month record. So it does seem possible that I could score a 25 mile PB with a tailwind in the Fens during the year record (It's only 1:03 something, done in 1993 on a windy day on a road bike with no tri bars, so pretty helpful to have the bar set so low)
You do make a good point though For a week record with the same rules as the UMCA year record, you could ride across a large land mass with a tailwind all the way and full support crew. Austarlia or USA might be a good place.
I thought about that for the year record but the logistics aren't easy and it would be extremely expensive even without a follow car. You'd need to be sure of a good enough tailwind to iron out any hills or mountains or find a flat enough route. Then, you need to get back to the start ASAP once you run out of land, into slow going conditions or run out of tailwind. That would mean a flight really, preferably by private jet which can carry your bike safely. With charter flights, you'd really want a bike waiting at the beginning of the route and have it arranged for them to be relayed back to the start of the route.
I do have it in mind to use my 3 free goes at the month record during the year. But I do have to give at least 21 days notice for each attempt, which I'd have to do for an official week record (if it existed)
Month record pace is pretty much year record pace. At least I hope it is because I was doing 236 mpd when I did the month and that would probably get me the HAMR by about 1500 miles.
I think that Gethin Butler matched or got very close to his PB for a 24 hour when he got the LEJOG record. Very hard terrain but he had a very good tailwind.