My DD is 9.5 months and I recently found that she can only really do 2 to 2.5hrs during her first A. Usually, if I take her up and start her nap routine the minute I see her first eye rub, it is 2 hrs sometimes even less, and then she'll sleep for sure for 1.5 hrs. If she is OT it's 45 min on the minute. I would try shortening the first A time.
I try to go by her cues rather than the clock but if she hasn't napped well and she is losing it earlier in the evenings, I'll put her to bed early too. For her it doesn't affect her morning waking, she always gets up early (5:00am BF then try for another hr) even if I put her to bed late.
Good luck.