Does the top cross piece really work as a "sort of" roll bar? I haven't seen any tear downs to know what is actually inside, and I certainly am not planning on rolling my baby.

Yeah it does. Someone here's got a collection of crash pictures. And I'm sure someone has a picture of the roll bar exposed.

Here's a pic from the factory manuals.

yes, i have seen pictures of rolled-over 914's.

the targa-bar actually worked very well preventing the cabin to collaps ...
Andy

I flipped my parts car over to remove the suspension and it didn't even phase the roll bar. The windshield frame didn't even hesitate to bend though.