I have a 30/31" waist and on my S/M, I cinch it all the way until the waist belt can't be tightened any more, and it's about right. 32" should be okay if the M/L's size is the same.
Craig: What I do is pack my quilt sort of loosely (not crammed down at the bottom in a stiff block), and put my food close to my back, with my insulated jacket between the outside of the pack and my food, so it goes: back > pad > food > jacket. It shouldn't be packed so tight that the pack is bulging out or stiff, just barely tight enough to keep everything inside from moving around, and then the pack can settle around your waist and conform to your back instead of being a straight stiff brick. You should be able to push the back inwards fairly easily–I know if I pack mine too tight, it tends to keep its stiff shape and won't bend with my body, which makes it ride upwards. Also, making sure your posture is good, with your back straight really helps keep it on correctly.
Hope that helps, it's a really comfortable pack once you figure out its quirks.