Can someone please tell me either from tried and proven experience or at least from a well educated stand point, how high can I raise my backseat and it still be suitable for an adult to sit in? It has to be raised to fit over a subwoofer box that was just put in but does not come from the factory.
If you really want to raise the seat then I would use a spacer under the seat brackets. I have used this method many times to gain extra clearance over subwoofer boxes that are too tall or not designed very well. You will need longer bolts that are Grade 8 or Grade 10.9 hardware.
Normally I can raise the seat about an inch with spacers and gain the necessary clearance. When I say spacers I don't just mean a single spacer under each bolt. That will not provide enough rigidity in the seat bracket.
The material I use is 1" square tubing with a .125* wall that is available from Lowes. I cut the tubing the same length as the seat brackets and the drill my holes. I weld caps on each end of the tubing to close them off and make them look clean. I grind and sand down the welds and then prime and paint them black.
I normally have 3 or 4 sets on the shelf just in case.
