Thanks, all. I think I agree that just raising the battery box up is probably the easiest solution. The current mounting point is in the ideal location (32") so I'd like to not mess with that.
Might try to do something with some angle iron and bolts as I don't have a welder.
Or maybe...this is a good reason to buy a welder
I suppose that I could even just cut some 2x4 material and use some self-tappers or bolts to mount them on edge. That'd get me high enough. Then it'd just be a matter of holding the battery box down to the 2x4 frame.
Nah, welder!