amom - I think she may need that AM nap capping. IIWM I'd cap at 45mins to start with, and shorten the following A time to around 2.75-3hrs. Whether you cap the PM nap is down to you. Some mums let their LO's sleep as long as they want, others will wake them. I am one of the latter, b/c if I let my boy sleep he will do a monster nap & then sleep less than 10hrs at night. I think if you choose to let him sleep & he goes longer than 2hrs then you just have to be prepared to give him a really good A to BT (so may need a later BT) as if you don't you may find he still does a short night & either wakes early or NW's. I'd give the 45min nap a try for a while & if the NW's don't reduce then I'd cap at 30mins.
gwcarnes - gosh it must be hard with twins on different schedules so I understand why you are trying the 1 nap! If your LO's are pretty easygoing, they might just manage the switch with no problems. However, just keep a really close eye out for OT b/c it can hit them very quickly when they switch to 1 nap. 6hrs A is a long time to nap when they first transition, ideally you want to be aiming for around 5ish hrs to start with but I know this morning with the EW it can't be helped!
In similar position myself with 5.30am WU's ATM & we have already transitioned to 1 nap ugh! My LO is touchy & VERY sensitive to OT & as soon as he gets a little OT then BAM! we get EW's. So we've pulled our nap a bit earlier to 11am for a few days & are coupling this with EBT at 6am. Means we will have to push the nap out all over again, but with EBT he's gotten more sleep last night than he has all week. Hoping for a decent WU tomorrow!