Looks great. Looking at your vidio it looks like the pivot low for the handle will make it hard to ballance, if you could make it go forward and back with rotating handle grips that would alow you to lock down the lower pivot point making it easier to ballance it when you drive. With the drive set up it is going to be fast so hold on. check ours out at
http://team1322.org/joeway.htm we used caster for ballance. Good luck. Looks like fun.