>>>Do you think it is possible to take out the seat rails and hardware and bolt the seats directly to the floor? <<<
- There is no good way to get the stock seats lower to the floor. The seat rails are only about 1/2 inch thick from the factory
>>And/or Have you heard of anyone having a seat shop modify/take out some of the stuffing to thin out the seats?<<
NO
>>Or, Do you know of any aftermarket seats like Corbeau or Sparco that would work and offer a little more room?<<
The only solution that makes a significant difference (over an inch) is to purchase the Porsche GT3 seats and the Brey Krause mounting kit for GT3 in the Boxster
http://www.bkauto.com/porsche/r9080.php
This is good for lowering your seat and the top of your head. I think the difference is 3-4 inches (your only hope besides and oversized custom roll cage if you take your car to the track.)
GT3 seat plus bracket costs about $1600 per side, so it isn't cheap.
There may be an aftermarket seat plus rails that will lower 1.5 inches, but it is hard to find any reliable data.
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One option to consider is the 'center console delete kit'. Removing the console from the side of your leg (where the shifter is) is considered more comfortable by vertically enhanced drivers. I think this costs about $200 and 4 hours of work.
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