Slingshot switched to a higher quality epoxy for their fins in 2009. Also the fins were made a tad wider and use slightly larger bolts too.
2007-2008 use the older red and black fins. the cheaper material, thinner bolts (smaller threads), and the flex of the board constantly bang-banging on the fins caused them to strip out easily.
If you get the newer slingshot fins you will need to drill out the fin holes a little wider (1/4" i think) to accept the new bolts for the fins.
A while back I decided i'd go all out and get aluminum fins that would never give me troubles again. they were pricey, but to me worth it (especially during a discount period). if you'd like to do the same i recommend cdi fins
(low pro 0.7 or 1.0)
You will likely have to drill your fin holes for these too. they have hardware for the smaller screws, but they are far apart for hyperlite, not slingshot. CDI Fins are slightly curved and fit almost perfectly flush. another great benefit about these fins is that the wider base of the fin and hardware make it so you wont put dimples in your board when tightening the screws as it spreads out the weight. SHINY TOO
there are some pics on an old thread here when i first got them. you can see the cdi fin and the slingshot fin (newer one) side by side for comparison