So I've decided to finally do some work on the styrofoam cutout I bought from a foam company in Midlothian, but I'm not exactly sure how to go about it. What would you recommend using to coat the foam for protection? Also, The piece I had cut is basically square all over. I'd like to cut/round corners and edges to make it tread through water easier.There's also an aluminum rod through most kickboats I've seen, how in the world do you do this? Any help would be greatly appreciated!

Just bumped up a old thread that will give you some reading

You might be able to use a three-quarter inch threaded rod instead of the aluminum piece. The hardest part will be to keep your drill bit extension Square so that the bar is level all the way across, and also making 4 inch washers to tighten down on the foam. I used a piece of old water hose to keep the threads from biting into my feet when resting there. My design used 3 threaded rods and 2 pontoons cut from an old foam doc that had a coating already and it was high density foam which didn't chip off as much as the lighter stuff. And elastic paint coating might be the best way to go to reduce the chunks chipping off.

Thanks for the info! Do you by chance have pictures of the one you fixed up??

No pictures, that was over 25 years ago and I discarded it quite a few years back when foam was banned from some Rivers. The immersed part foam wycked and bled saltwater where I was using it, and it took a day or so to dry out, so everything had to be stainless steel or aluminum Plus no transporting inside a vehicle due to corrosion smells and wetness. Any bumps caused Dent or knocked chunks out so I couldn't use it on the river or around shallow water. The positives were that it was strong and solid and did not ever leak like inflatables. Also it was faster then the ww because of separate pontoons and easy to build with the two pontoons lined up it could be easily drilled for the threaded rods.

Here's a picture of some I use to make for fun. Sold the last 2 when I picked up a couple well used water wagons. They fish just as good as a water wagon except no motor mounts which I have never used.