I bought Coosa to do the floor and transom in my '79 Starcraft Super Sport thinking I was getting an upgrade to plywood. I bought it from Boat Outfitters. I learned a few lessons that hopefully will help you:
1. The website says to use Coosa in the same thickness as the plywood you are replacing. Based on that recommendation I bought Coosa in the same thickness as the original plywood. I believe this was mistake #1, as the Coosa flexes significantly more than plywood. I don't think anyone is going to put a foot through the floor or anything like that, but it bothers me. This was especially disappointing when it came to the transom, as I expected the composite transom to end up stronger than what I'm replacing, but at 1.5" thick (3 pieces of 1/2" laminated together) it still has more flex than I expected.
2. It is not pleasant to work with. It cuts easy, and I was able to shape it with a router pretty easily, but it made a terrible mess. Even working outside I had to wear goggles and a respirator due to the dust. I'm sure someone here will say that I should have known that anyway, but it was just awful to work with as far as the dust goes.
3. It is crazy expensive, especially if you have to have it shipped. I had it delivered in 4x8 sheets, and I spent over $1800 total for 4 sheets.
I have not done the floor yet, but after getting the transom done I really wish I would have just spent the time to get plywood, and seal it with epoxy resin, over-drill and fill holes, etc. I think that will end up lasting realistically as long as my expensive composite floor/transom, would be a better direct replacement for the plywood that was there, and far less expensive. More time-consuming than just dropping in the Coosa, but I think I would have been happier with it. Bottom line, if you value your time above all else (and some weight savings), go with Coosa, but go thicker than the original plywood. If you want to save some $, just do plywood. Seal it with epoxy, take the time to over drill any pass-through holes and fill with epoxy then drill to the correct size.