my 7 month old DS always amazed me with his ability to go 12+ hours with maybe one little 20 minute cat nap, and then have a totally fitful night.
But I finally did discover his natural nap times and that has helped. IMO if they are taking very short naps, it is because they are very tired and not having the full sleep cycles they need at naptime or overnight.
i agree that some babies just seem to need less sleep, but 9 hours of night sleep sounds very light to me. are you sure he wouldn't go back down for a couple of more hours if you give him a feed then?
And is this 9 hours with any feeds, or not?
our sleep schedule runs like this:
8:00am ish - up for the day
11:00am ish - 30-45 minute nap, very occasionally as long as 1.5 hours
4:00pm ish - 30-45 minute nap. have tried to move it forward to 3:00 but not much luck. sometimes skipped entirely after much screaming and he then is dozing off around 6pm.
8:00pm - asleep after feed starting at 7:30.
we give one bottle at 10:30pm and then he wakes for at least one BF, usually around 3am or 4am.
I also have to wonder if keeping him up late is messing with his inherent sleep pattern. Not to get all sleep book about it but there does seem to be a strong case for babies having a natural sleep cycle of roughly 7 to 7, give or take an hour.
We used to keep DS up until 9 or 10 and things seriously improved when i moved back his bedtime. Means he doesn't get to see DH most evenings, which is a shame, but in this case he did get cranky.
also agree grizzling before sleep is very normal. like i said, once i realised when he needed his naps, he almost always will fall asleep, even though he might moan for 15 minutes or so.
good luck.