DUH !
Always check for additional pages before posting.
Still think 1/2" lexan would be enough to do it in one layer. I have some & will help you out with a bit of it if you like. PM Mailing addy & your size needs and I can cut it to near your size needs while leaving you some to work with.
Price is high though, finished pics & performance report here.
BE
edit: I have no idea how long it will take to cross the lake. I would think it would be there in time for the Tt cooler if you were to reconsider using it.