an old trick which may help if the riser is needed temp' while you build up back muscle say, is to push small bits of the thick dense foam
(or in ye olde tymes a bit of foam carpet)
under the front part of the saddle padding, along each side in the gap where the padding cover folds back and you can get your fingers in.
as you can tell i have had experience with having to make do rather too often over the years, & having worked for crab tight school owners who would short cut, short cuts to save a dime you pick up some tips on how to & how not to.
i have an ancient saddle with a *fixed tree of the old type so it sits very still on the back which i use for the early saddle introduction stages, the stirrup bars are bust but for lunging etc its ideal, it has carpet padding added & weighs a ton, but if anything were ever to flip & break it - at least i won't cry over the loss!
*fixed tree saddles don't flip up off the back at the cantle end when not mounted like spring tree saddles do.
bye