Not sure I'm in the best position to advise as our naps and wakeups are nowhere near consistent, but we're generally having most success with a set nap at a time that works for us, and a fairly set BT with option to go a bit later on the rare occasion we get a good nap. I mean rare - probably three or four naps over 2h in the last couple of months!
So we do:
WU whenever, was in the 5 something's for a long long time but now more likely 6.15-6.45
Nap set at 11.45 give or take a few mins - usually 1-1.5h, sometimes more, sometimes horrendously less!
BT 6.15-30pm, very occasionally later if she pulls a really long nap
I've kind of accepted that with the constraints we have (nursery 3x a week, nap fairly set at that time) then short nap and longer night is probably what we're going to get. Regular 2h naps aren't likely here!
From what you've said, it looks like longer morning A gets you a better nap (even if you have to resettle) so how about fixing nap at 12pm and see how you go?