I have a new Permobil C500 with the 3G seating system, and it's tearing up my lower back with serious skin problems. I think most of the problem comes down to the fact that the cushioning on the back doesn't go all the way down to the seat pan, it stops about 8 inches above, and the rigid metal back underneath the cushion stops about 2 inches lower than the cushion, so there are two edges which my back can rest on with focused pressure.

I thought lowering the rigid metal part of the seatback and ordering a longer cushion could solve the problem, but from reading the user manual, it looks like the back can't be lowered more than it is, only raised. It seems I need an aftermarket back.

There are many offerings, but very little way to anticipate which would be best, and which has hidden problems. Has anybody had any experience with a particular seatback which they can recommend? That or any other advice would be most welcome!