Hi, I have been moving to 4hr EASY too, but trying to extend awake time with my lo just made her over tired and cranky and messed up her night sleep as well. It has taken me weeks to sort it out, and have gone back to reading her sleep cues and it has worked out much better. If she gets up at 6am then she will usually be back in bed by 7.30 and then will usually sleep for nearly 2hrs. So we do about 1/2 - 1 hr of activity time before the next feed usually. This works fine, so don't get too hung up with having the exact same routine that is in the book which is only a suggested routine anyway. Follow your lo and she will let you know what works for her.
At first you may have some feeds that are quite near to nap time but as long as they are not feeding to sleep it is ok. Just stick with the 4hr ish eating and the naps follow in my experience.
Our routine is something like this at the moment.
A - 6
E - 6.30
S - 7.30
A - 9.30
E - 10.15
A - 11.15
S - 11.30
A - 1.00
E - 2.15
A - 3.15
S - 3.30
A - 4.15
E - 6.00
S - 6.30
Gradually, as the naps get better, the baby naturally extends their awake time. It is certainly a bit hairy at first! My lo would have a couple of feeds close together in the middle of the day and I didn't know how on earth we would get there with 45 minute naps, but we did with a bit of patience and watching her like a hawk!
HTH