In reply to crustypunkuk:
I'm 5ft2" and often have fun finding sacks with short enough back lengths that I can fill them up and still wear a climbing helmet etc. If it helps, the 2 sacks that I've found that fit me are:
* Deuter Pace 28 SL - basically, a women specific light weight sack for ski touring / walking etc - comes in black and mint green with a girly flower attached. Possibly a bit smaller than you'd want but Deuter do various other womens sacks so might be worth a look.
* Osprey Talon 35 with S/M back length - my year round hillwalking sack - now seems to have been replaced by a women specific model called "Tempest" and would appear to come in various "girly colours. The Tempest comes in 30/40L versions. My 35L one has loads of room and easily passes as hand luggage.
Post edited at 14:03