I've done this before, fairly easy to acomplish, but I'll share with you what I learned through trial an error. Some of the wakeskate fins have more depth and a nicer shape than the long low wakeboard fins. Although I liked the Liquid Force 1.5 WS fin. http://www.the-house.com/wk8lfsktc156zzliquidforcefins.html
Most of these fins have three drilled and tapped 1/4" x 20 holes. LF uses two of the three holes for thru bolts, while the other manufactures use 1 thru bolt and two studs that are sunk into a small indent in the board.
Even with a drill press, three holes are tougher to align than two.
As is stopping the depth for the plugs. Using masking tape, tape the top and bottom to avoid any splintering of wood, foam or resin and to draw on without messing up the graphics on the bottom. Measure the two holes on the bottom and align them with a centerline measured tail to nose. Just draw that on the masking tape. Once your holes are marked, drill through and like I say, go with 2 and not the 1 thru and two NOT thru and 1 thru.
Remove the tape.
Seal the inside of the holes with a good quality epoxy, making sure that your 1/4" - 20's still slide thru. I wrapped my screws with a small piece of polyethelene and left them in while the epoxy cured for a perfect fit that pulled right out.
Viola, a wakesurfer.
Good luck! It would be great if you'd post up pictures of the modification.