The Tiger is probably about 4,000 pound heavier than a SMB. Also, I don't think you could run the AC very long on the batteries. 20 amps for an AC at 120 volts is 200 amps at 12V roughly. I think I have 200 AH worth of batteries, so that's only an hour of usage. Kind of the same thing as trying to run an electric heater. It works for a bit, but not much. Even my toaster pulls things down pretty quickly. I usually start and run the engine for a few minutes when I use the toaster.
2008 Ford E-350 Quigley 4x4 V10 - 164,000 miles
RB50, PH Top, Dual AGM Group 27 Deka, 2000 Tripplite Inv., No Propane or Water Systems
Van Weight 8,100 pounds, added one rear leaf spring, BFG AT KO LT265/70R17 E Tire press 50psi.