In times past women wore bustles. That style appeared more than once through the years.

Perhaps you can revive it, only for men this time.

One good thing is that your kilt can actually be tried on before you make that daunting cut. If it feels as thick and uncomfortable as mine did, it makes it easier to make that cut.

Then, after it is too late, try it on again and hopefully you too will agree it fits better and doesn't feel as bulky.