Ryan,
Glad I'm not the only one who thinks Propex + portable propane tank is a good idea. We'd like the heater, but won't use it enough to justify the hassle (and ground-clearance penalty) of a fixed underbody tank, so I was planning to do the same.
Regarding the battery, probably better safe that sorry. 'Course I went the other way and I have an AGM inside the cabin, so there's always a choice to be made.