Does your friend have a waist that "has no hips"? I guess that would be no waist, either.
Folks without a waist/hips indeed usually do have a problem with standard weight belts. I've taught quite a folks with this problem.
There's only three solutions I know of:
1) See if you can craft a carefully balanced rig that has no ditchable weight. Usually, it's only possible with a very narrow set of equipment. I do some mentoring, and one thing I do to teach balanced rigs, is have folks swim up a series of weight belts. I consider myself in great shape and use heavy, high-thrust paddle fins: I can swim up 10 lbs easily; 20 lbs for unlimited distances with a huge RMV; and 30 lbs only for a short burst of 15 feet.
2) DUI makes a "weight belt with suspenders" they call a Weight System or something like that. Here's what it looks like:
3) You can attach integrated weights to the plate. Halcyon makes these. Apeks does, too, and their system, although nicer and easier to use, is a PITA to install, let alone find from a dealer.
Hope this helps - the problem is more common than you might think.
All the best, James