1" is probably overkill - heavier and more expensive. Standard 3/4" ply will be fine especially if you are epoxy coating it. I also agree that removable is key! Rather than make countoured ribs just block the floor in a few strong places (sidewalls and centre of keel) that will save you hours of messing around!reb said:I would be looking to do that too. I plan on using some 1 inch ply coated in sanded epoxy, just know it might be a pain to get the measurment from the ribs to the bottom ot the ply.