What year is your board? Chrome Dome Fins will fit the newer Slingshot boards when they changed from 3/16" holes to 1/4" holes. Let me know if you have any questions.
My '07 Recoil came with 1" fins. Last summer I requested smaller fins and they sent me 3/4" fins. Actually, it wouldn't be much of a problem to ream out the fin mounting holes from 3/16" to 1/4" in order to use the Chrome Domes.
Hey Paul, Yeah we have had several Sling Shot customers do that. Really easy to do. The board is made of closed cell foam so there is no worries of water penetrating into the board.