not sure you need it, my Koholo is 2 years old and I have not had issues with it leaking or bouyancy problems.  The interchangeable skeg boxes is a good idea, I found some good deals at http://www.theshapingshack.com/ on boxes and fins.

 The foam would just add weight.  It would help if you had catastrophic damage to the hull while in the water to help get you home, but that is unlikely.  the foam could also trap moisture inside the hull because you arent sure it will fill every little nook and cranny.  As far as the boxes go you can just build in some wood around the box which is stronger than foam and more water tight if you crack the box a bit from hitting a rock or something.  I think the new Kaholo plans and kits are using boxes now instead of glass on fins.  I built two Kaholo's about 7 years ago and just used the two parallel skegs which are fine, I dont think I would even notice a difference using different fin set ups.  If you go with a single box I would use the fins unlimited longboard box.  If you go with two fins I would go with FCS or Futures.  You can make your own fins for any of them or have a ton of choices to buy.  I am currently building an 8 foot Grain fun shape and used the fins unlimited center box and FCS side plugs all set in blocks of wood.  Search this forum for the older thread on boxes.  Wood Ogre has a really great way to do the boxes using foam and wood. More from the windsurfing perspective. The boards are a lot of fun and work great!

Thanks powergroove,

My thoughts behind this are two-fold. I'm going to be building a 17' center console after the Kaholo, and want to practice as many relevant techniques as possible that will speed up my future boat builds. I figured the foam would not only add strength and flotation, but provide a solid surface to inset the fin-boxes. It would save me the time and hassle of installing balsa or cypress blocks for fin boxes as others have done.

I'll be using the board mainly for fishing the coastal mangroves of south FL, so speed and weight aren't really a concern of mine. 

Tyler

Thanks SurferBill, appreciate it.