Just got mine 2 weeks ago got out once just getting use to it because i surf more off the front foot and the sub driver is more of a back foot board.you can always ask Matt Biolos on his blog he could probably give you the best answer..
5'8"-5'10" stock dims I'd say. If you ride it at your hight you'll have a very easy, forgiving board that will catch a lot of waves and make you surf very well. If you ride it below your hight you can get really radical and manueverable on those things but you'll sacrifice some wave catchability, which you might need a bit more in Florida. You'd be suprised how magically these lost grovelers catch waves. Final answer: to be safe I'd call it at 5'9" stock dims. A lot of maneuverability with a little bit of extra volume for catching waves. Matt's really good at efficiently placing the volume to get rid of any unneeded foam, but some losts pack a lot of foam. Don't be put off by this though, one of my losts is a 5'10" plank as thick as my longboard, and it surfs like a little skateboard... crazy rail to rail, huge snaps off the top, big finners and roundhouses....I don't know how he does it. Don't be afraid to size a lost conservatively. Even the big chunky ones turn on a dime. I highly recomend that you talk to Matt in person though. He's around every once in a while and sometimes he visits surf shops down there. Usually if you ask him a question on his blog he'll answer you. That guys really good with customer service, they go the extra mile. In getting to know him in person, I actually found that he's quite frankly just a chill dude. Hit him ump on the mayhem blog.
I have (had) both. Sub-driver works a little better around here in NJ.. I didn't like the BB too much. Felt it had a tad too much rocker for me especially in below stellar surf. Sold the BB recently on CL. Still have the Sub-driver for sale on the NJ craigslists (jersey shore, central jersey, etc.) for 300 OBO if interested. Need to sell to buy new boards for a trip. Has a some pressure dings on the deck and some sanding scuff on the bottom but the board still works great. Let me know if interested.