I'm leaving my qualification until the last minute, riding the East and West Coasts on the 20th June. I don't need to convert my pre-registration until the 23rd.
I know the route well, and I can train for it specifically, by doing local hilly rides, hopefully in good weather. There's a lot of flatland riding, punctuated by some long drags. The return to the control at Mytholmroyd at 375km allows a sleep stop at about the right time to allow the remaining 230 to be done in daylight. It's only 5 km over 600, and it can be entered at the last minute.
I might not ride PBP, I've been alternating styles between filming and participating, and filming from a motorbike. There are logistical problems to be solved, and not riding is the easier option, but it's not supposed to be easy, is it?