Raising Passenger Seat

[Iflylow]

I am trying to mount an amp underneath the passenger seat in my '01S. In order to retain full fore/aft range, I need to raise the seat by 1/2"-3/4".

Any problems with placing spacers underneath the mounting rails?

Alternatively, as it is I lose about 6" of aft travel. I can live with that, but is there any kind of adjustable stop on the electric seat control? If I can limit the travel and avoid damaging seat/amp, I'm OK with that, too.