Wow, quite the interesting discussion generated by this question. I probably should have given more specifics, but some of those specifics are not decided yet (ie: what's above the belly pan, what is the cabin going to look like, etc). Also, I don't think the discussion would have been as informative.
I didn't think it was quite as straight forward as it might have seemed. It does depend on several factors and now I can design better with those in mind.
FWIW, it's a general purpose passenger commuter type car. Battery electric vehicle with an attempt to make super light and the more aero the better.
My goal is to get 100-120 range on lead acid battery technology and keep hard costs under $10k. I'm even considering a PVC frame, but need to think hard about the structural integrity in collisions on that one. Or maybe a hybrid frame.
Anyway, this leads me to the next question which I'll post in another thread to keep the discussions relevant to the post heading...
How much surface wobble is ok?