Pack Question

I am looking for a small internal frame pack to use as a day-pack or overnight-pack, due to the fact of a back injury I find that conventional day-packs are uncomfortable after about 3-4 hours depending on how much weight is involved. So I think that a internal frame pack will do nicely now I know to get a good comfortable fit I need to try them on but I am trying to narrow down my search some what, the main things that I am looking for in a pack is as follows.

Around 3000ci give or take (about 50L if I did the math correctly)
(no more than 3500ci/57L no less than 2500ci/40L)
Torso length 20-22 inches
Built in hydration system compatibility
Decent ventilation at lest something not to hot to ware
1 or 2 main compartments with a couple of pockets is ok
No useless organizers like a lot of day-packs have or a ton of pockets
Compression straps
Top loading main compartment (to get away from a zipper on the main compartment)
No detachable parts for use as a fanny-pack type of thing

100 cubic inches bigger than what you asked, but still an awesome pack.

http://www.granitegear.com/products/backpacks/ultralight/vaportrail.html

ULA Ohm

Gossamer Gear Gorilla

Take a look at the Osprey Kestrel. I have the 38L and am very pleased with it. The 48L, which is pretty close to your target of 3000 ci and seems to meet most of your criteria, is getting pretty good reviews too.