[racer]

Subjectively, I've felt that the hardtop offers more headroom. I can't confirm if this is actually true though.

Its been many years since I had a Boxster, but I thought, hardtop or not, that the driver is subject to the "broomstick" test for DE participation. That said, I could see lazy folks not bother if the hardtop is in place.

I also wouldn't count on a 45lb piece of fiberglass and glass to add much to the chassis structure, and I would think in case of a rollover, the top would simply get smashed and possibly detach. I am not sure it offers much more protection than the factory softop in this scenario.

Spec Bosters run a full rollcage underneath, including above the driver, to protect in case of rollover. The Hardtop is used to cover the cage and maintain an OEM look is my presumption. Also, lighter and fewer parts than a full softop.