Becky, Have I got this right.
After a solid 2hr nap she did a 30/35min nap on 3hr15 A?
After an hour nap she did a 40min nap on a 3hr15 A?
Sounds like you 'could' be like us and get 40min naps when OT and try to resettle and cant and 30/35min naps when UT (but wake grumpy because still tired KWIM?)
If you get a 2hr nap again I would go for 3.5hrs. At 8 months we were certainly heading closer to 3.5hrs for A times after a solid nap. I think we had something like this...
WU 6
A 3hrs15
Nap 9.15-11 (this was always his long one and the one we kept in the 2-1)
A 3.5hrs
Nap 2.30-3.30/4
A 3hrs (Z liked a long middle A and short A to BT)
BT 7