That's what I did with mine, 1/2" as long as you have good support for it. I sealed with an auto grade fiberglass resin, after it dried I was impressed with the seal on it big time. I'm gonna go right now and carpet mine in about 10 minutes. I'm doing the wood in pieces and putting them in like panels with rivets so they could be removed in the future if I wanted. I've come to find out there's not many wrong ways to do some of this, just personal preference and some ways last longer than others.
good luck!