I'm frequently coming off of a low training base and jumping back into a 600+. For some reason, it's working less this time around - loss of neck strength and the fact my bike fit slipped has imploded the last few rides; plus a much lower average speed vs my past expectations; sleep needs.
For PBP, I went from nothing to a low volume of training and doing the SR series over 4 months, which went OK; and late last year a similar pattern building up to the 600/400 within a few days of each other.
10 weeks is maybe a bit short, but you should be fine particularly if you are on a recumbent, and put up with being a little cruisier at the start. Consider doing a 600 in the *middle* of your training regime, to discover all of the little pain points ahead of time and not go into the 1200 fatigued.