Have just discovered this thread and so answering a few references to the 6C SR. But firstly congrats to Will for setting this up - it takes a lot of work to get everything validated. I'm also impressed with the lack of overlap between the two routes as its actually hard to get a sensible route with that amount of climbing
The 6C does have a AUK Permanent version. So far it there have been 2 or 3 entries for this - but I'm not sure that anyone has actually attempted it seriously. There are a few riders out there who could manage 10K+ of ascent in Welsh lanes and get some sleep, but only a few. I rode the 4C, on which the 6C is based not long after waltzing around the Rough Diamond 300 at the head of the field. I was probably in the best nick I've ever been. Extrapolating my time on the 4C (in which I had 3 15 minute catnaps) to the 6C, I would have had about 2 - 3 hours spare for a sleep but would have probably been too worried about missing the time limit to complete it. That's why the SR approach, with 60 hours makes sense.
There have been 5 finishes of the 6C as a super-randonnee, most of them have made near full use of the 60 hour limit, and most have struggled to make their planned overnight stops. If you think of 3 hilly AAA 200s back to back, if you take 12 hours for the first, you will take much longer for the third...
But the completion rate is much higher than the 400 and 600 Cambrian Permanents - precisely because there is the chance to have a couple of sleep stops. And the feedback is that it is a highly rewarding challenge that it is uniquely different from anything else that Audax has to offer.
