There is some truth to the problem you describe. My own three measurements (true waist/ hips/ tush) are of descending sizes. I am told this makes it very easy for the kiltmaker, since everything hangs rather nicely from the largest/ highest measurement, BUT (not butt) it means that to keep it on, I need to tie it VERY securely around my "true waist." That in turn does make it hard to breathe, and on the flip side, if I suck in my gut, the kilt falls off!

SOLUTION: (recently found) keep it a bit looser around the true waist to facilitate breathing, and wear the sporran with a strap fairly tightly around the hips, just as I do with my trousers. Result: I can breath, the kilt doesn't fall off, and the sporran hangs at a reasonable height, obscured from above by my tum-tum, thus even allowing my clerical robes to hang straight over the sporran!

Ta-da!

(Disadvantage: It may make it trickier for the kiltmaker to measure. Sorry John!)