Clearly 10.5-11hr days are advised at the beginning of this process so I can't see how you can continue with NNDs if nap days make night so short and bt so early.
This is a common idea but I find if you add up what the total sleep in 24hrs was (nap plis night) before the drop it can give a closer idea as to the amount of night sleep you can aim for after/during nap drop. For us it was 12hr sleep in 24 (2hr nap + 10hr night, nights reduced to a silly 9hr or less during the move to no nap).
For you then I would aim for 12 hr total sleep too, seeing as naps were 1hr plus night of 11hr+, if he needs more he can wake later in the morning.
How about do nap today, late BT (expect 10-11hr night), FX for a later WU and go from there tomorrow?
Do you feel he can cope with NNDs? And do you feel he can do it once or twice per week or every day? (I ask because mine clearly needed his nap, when I initially tried NND he was a danger to himself, literally falling down at 4pm, we did better with 2hr nap and short night for a while).
YK there are a number of option with the 1-0 so it really depends on what your LO can manage...but I would say you do need to expect him to sleep less in the short term, he's already started the transition so 1hr nap and 11hr night is likely not possible for him to maintain, his sleep may not extend until he starts to get into the new routine.
