I think I'm going to just do what Mike does (for now) and bring some 5 gallon jugs with me when I go to Sebring.
I think with 2 5 Gallon jugs, that should be just enough for 4 track sessions, give or take.
edit: Actually, since I have the Zenclosures sub box, I'm not sure I can fit 2 5 gallon jugs in my trunk.