And if the large is not quite right either... you may want a pack with adjustable harness. Packs like the Granite Gear Nimbus series will be light, but also adjustable in inch increments. Aarn packs are also incredibly adjustable in just about every way possible. Some Deuter packs and the heavier models of Gregory and Osprey will also adjust somewhat. But those "ultralight" (they are not really so light as they want you to think) Osprey packs are impossible for some people. I wanted to like one that I bought and could not wear it without back pain. With no way to swap the hip belt or adjust the back frame, I had to find another pack. It turns out I am on the long side of short and the short end of regular sizes... most regular/medium packs will sort of fit, some small size in other brands will sort of fit... I have the best luck with a pack that will allow me to set the shoulder harness by increments.
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzukihttp://hikeandbackpack.com