Activity times too short for a 4-5 month old.

[Fudge]

My LO is 4 month,3 wks old and has been on the 4 hour EASY for a few weeks now,its going well as far as eating goes,she has no problem eating every 4 hours.The A & S part is the problem;she wakes at 7am and is back to sleep at 8 am till 8.50am,then its too early to eat,so shes doing A time,but seems to get tired again within an hour or so.She naps again till time for her next feed which is fine,but will only again stay up for about an hour to 1 hour 15 at the most on each A time.She wakes up happy from her short naps,so I can't extend them as she really wants to get up then,I've tired WtoS,PUPD,but they didn't work.Heres her routine at the moment:
 
E 7.10am
A 7.40-8.0oam
S 8.00-8.50am
Y
E
A  9.50-10.15am
S 10.15-11.00am
Y
E 11.00am
A  11.30-12.45
S  12.45-1.15
Y
E
A 1.15-2.30pm
S 2.30-3.20pm
Y
E 3.20
A 3.50-5.15pm
S  5.15-6pm
Y
E
A 7pm bath
E 7.15
S 7.45pm to bed
Y

I'm in a cycle of too short naps which mean she can't stay up very long,so she has to nap again twice between each feed.What should I do?

[Mom to M&M]

What happens if you gradually extend her awake times? At her age, she should be able to stay awake at least 2 hours - so you'd prefer to have that morning nap start at 9 am, not 8am. Can you extend her A time by 15 minutes every 3 days, maybe taking her for a walk, giving extra cuddles during that time, etc?

[Fudge]

When I try to extend her activity,she gets very cranky and starts to cry.She blows a raspberry when shes ready for bed and if I don't get her to bed asap,she goes downhill fast after that.Pram walks don't work when shes tired as she just cries,the only thing I can do then is walk around whilst carrying her.However,I will try to extend again even by 5 mins at a time and see how she goes.