Nick Tomsyck has the best idea. Actually, I'm finless too, but probably not for very long.
Slingshot fins, at least the '07's, are made of pretty soft material, and the threads are easily stripped, if over-tightened, or otherwise abused. However, there is a product called Heli-Coil,
http://www.helicoil.in/helicoil.htm which can be used to replace the stripped threads. (This is assuming that the fins are thick enough to withstand having oversized holes drilled into them). My 1" and .75" fins are still in pristine condition, so I haven't tested this out.
The heli-coil is a thread insert that can be placed inside the fin after drilling out the holes in the fin and using a special heli-coil tap to re-thread the holes for the heli-coil insert. Once the heli-coil is threaded into place inside the fin, the original screw can be threaded into the heli-coil and the fin can be re-attached.