I have found an easy fix to counter the stiff seats bro.
I have this habit of having all car seat covers custom made from fresh material (mainly because off the rack options never appeal to me). And I ask them the amount of foam that would be required to line all the seat covers in square metres (0.5" to 0.75" foam thickness). Then i rush down to the nearest molty foam shop, purchase the foam myself and hand it over to them.
The seats end up being much more comfortable with quality foam lining as opposed to the thin foam lining most accessory dealers use.
This is a tried and tested method