After recently cutting a stock Boxster piston in half to do a cross sectional study on it, I'd say it would not be very kind at all to the cylinder pressure increases associated with fogging the engine...
Turboing the Boxster is certainly the best all around way to gain performance.. The Turbo specific engine combination we are developing now, coupled to the cylinder upgrades is sure to make serious power, reliably.
Jake Raby
www.flat6innovations.com