I am not sure that light is the answer.
A heavier wheel will effectivley lower the vehicle center of gravity.
It may also store some inertia on the 1% WOT assults on the hills.
I know it will take more to get the initial weight moving but there are pros and cons.
I also feel durabilty should be a major consideration.
A smaller diameter rim moves the wheel farther from danger.
17" Rock Monsters FTW!!!!!