Hi, I just posted on your EASY thread too
If LO is overtired then temporarily allowing some slightly shorter A times can be a good way of allowing them to catch up on some sleep. However, you are reaching an age where the 3-2 nap transition tends to begin and that can get quite complicated quite quickly with lots of Mums falling into an UT/OT trap (been there and done it!!). By that I mean LO starts having short naps because they need a bit more A time, but ends up OT because of the short naps. Mum shortens A time because of OT, leading to more UT short naps and the cycle continues.
I can probably help you more if you post a recent day or two in EAS format?
The other thing you mention - using PUPD to get rid of a night feed - I realise now this may have implications for your post on EASY about frequent feeds in the evening. How many night feeds does your LO currently have and do you do a dream feed?