I have the similar waist/seat measurements although I have not had the problem you report. My big problem is that the left hand bottom apron edge lifts badly, which I'm sure is 'compensation' for the top of the kilt being pushed out by my belly. To this end I had the lower hip strap removed which does allow the apron to hang better. When measuring for a kilt the seat (hip) measurement should be loose to allow for comfort when sitting down, so maybe a bit more leeway here would help.