Here's the first hip belt I made, which I don't like. The foam in it is only 26" long (the hem makes it slightly longer), which would probably work for me, but not many other people. More importantly, it's shy of 3" wide, which I don't think will be supportive enough, especially in the lumbar region. I'm still working on it, but the next version will taper from 2.25" at the ends all the way up to 4" in the lumbar region (plus hems). This widest part will be 8" long before it starts to taper.
I've got another quick question for people who have made a pack before. Do you prefer to sew the webbing directly to the padded part of your hip belt or to have it run through loops (like the belt loops on a pair of pants)?