Cutting foam for seats?, any suggestions. Options

[DougC]

I'm doing custom bolsters on stock 914 seats and need some help. I'm using wire bolster frames from stock BMW seats from my M3 (they were really raggidy). I've mounted the frames using screw head machine bolts and nuts attached to the stock fiberglass. I will be slathering on the Bondo at all the attachment points tonight and letting it set up for a couple of days. Then I plan on doing final adjustments with a propane torch before adding the cushion bolster pads, to get the angles right. I will be using the stock BMW cushions which are(seem) huge. I've started to "shave" them down using an electric knife (probably a cheap one) and it's chewing the cushions up a bit, like it's not sharp enough. I've also used a razor blade without great results. This elec. knife is brand new [got mother-in-law's permission] BTW. I fill confident in my ability to get the contours just right as long as I could find something to cut with. Any suggestions? Here's a preliminary pic of the framed seats.

Doug C