I removed the upper air box completely and installed two 120mm ball bearing 12vdc fans...reinstalled...no addt'l baffling, no thermostat. Air blows out the chimney unrestricted. Those two fans and four small fans that are attached to my refer cooling fins are the best mod I made to the whole RV. 31 degree fridge at setting number 4 always. Runs on propane while traveling and NO CHIMNEY FANS...it runs at least as cool as camped. Make sure air will pass unrestricted thru chimney with and w/o fan operation and you'll be fine in any situation.
2014 XLR 415AMP, 2011 F350 6.7 DRW, restored 82 Wing, 02 Shadow, 06 ST1300A, NRA Benefactors.