I use a Noah Tarp 9 and it works just fine. I've been in storms with it and stayed dry too. The only time I need a larger one with doors is in snowy weather when it's blowing sideways. And I don't think you'll have that issue in Florida!
If you're trying to save money and want a full coverage tarp, check out the Chinook 12X9.5 I'm doing a few mods to mine by adding extra pull outs and sewing grosgrain pull outs over the gromits. They are around 35 bucks.