I'm with you Burke -- tented hand = injury!
A closed slap that involves the grabbing action you describe is a good approach to getting a crisp, clear sound. It's how my first teacher, a cuban rumbero, taught me. After a while I didn't need to work at 'grabbing' the head, the sound was just there.
Keeping your hand flat will also allow you to transition that closed slap to an open slap -- IMHO both sound best when approached with a flat hand. With the open slaps I keep the djembefola advice in mind i.e. 'open' fingers/hand, which I've come to understand actually means relaxed hand so my fingers can flex a tiny amount after my palm hits the drum and so they then bounce immediately off the head.
Time flies like an arrow; fruit flies like a banana