Hi. I'm no expert, but thought I could help. If Lo wakes early and he isn't hungry yet, then I would definitely wait til the feeding 'time'. If the nap is too short and you've tried extending and Lo just won't sleep more, then have a quiet A time before the feed.
What I do is keep the feeding on time, and try to keep the other stuff too, but it's life so sometimes it doesn't work. Just count awake time. For example if he woke at 1030 and is due for a 1100 feed, I'd have A time but the next nap would be 30 min earlier than normal (or less if he shows tired signs earlier)
And as for the 'stretching to 4 hour Easy' I think we started the switch when LO was 3.5 months old. Everyone is different, but if you're having trouble with shorter naps, that could be it. If you look in FAQ on the EASY board it has the 'guidelines' for switching over.
Good luck
Kristi