Florida is flat as a pancake and hot and humid, even in December. You might like that kind of weather being from Oh-Canada, especially in December, but to me it's not worth it to trailer a Boxster to this destination except for the fact that you could purposely stop in North Carolina and drive the Tail of the Dragon on your way to FL
I concur with BYprodriver. Save the money on trailer rental if you can't borrow one from someone (and you should be able to borrow one if you start asking around, or at the very least rent it from an individual for much less) and use that money to rent a really fun convertible while you're there.