Lowering Standard Seats?

I find my standard drivers seat a bit high. Prefer to get the seat very low and up right. Is there any way the sub-frame could be lowered?
 
There used to be a fudge on older Clios where there were spacers underneath the rails that could be removed. Although it snagged on the carpet a bit.

Have a look?

Otherwise, don't mod the subframes, they need to be strong and you'll compromise them I'd assume - work out how they're mounted and buy aftermarket/custom.
 
some italian company manufactured 197 specific subframes that were lower than the original ones, but I remember they were really expensive....