1 hr naps during the transition often indicate UT, so it may help to increase A time a bit.
Our routine during the switch was constantly changing (as you all well know), but here's a couple we had:
7:30 - wake
10:30 - nap #1 (this was when we first started the switch)
12 - wake (on her own)
3 - nap
4/4:30 - wake (on her own)
7:30 - bedtime
Then I kept shifting nap #1 by 15 min each week and shifting the pm nap by 15 min and cutting it by 15 min....so when things got challenging (at 4 hrs of A time) it looked like:
7:30 - wake
11:30 - 1/1:30 - nap (I let her sleep)
4:30 - 5 (or sometimes 5 - 5:30) catnap and I woke her
7:30/7:45 - bedtime
Then as we kept moving that first nap, she started refusing the 2nd nap so we did:
7:30 - wake
12 - 2 nap (woke on her own)
7 - bedtime
I knew she needed a minimum of 2.5 hrs of sleep, so if the first nap wasn't 2.5 hrs, I'd try a catnap at 5, if that was a bust, I did bedtime at 7.
Once we got to one nap it looked like:
7:30 - wake
12:30 - 3:30 (and sometimes even 4, I never woke her)
7:30 - bedtime
Even then, she could only do maybe 2 or 3 days of one nap and then some OT would build up and we'd throw in a 2 nap day (back to the very first routine) to ward of EWs.
It took us about 4 mos to get fully on 1 nap. I should note that she is a textbook bub, so that made things easier for us.