My 2 cents... (Don't take this as discouragement!)
I understand choosing an Insight for its light weight (1850 lbs) and aero efficiency (Cd .25, small frontal area).
Seeing how much fabrication you're in for, I think I might have opted to get a 95+ Metro and chop/taper the roof, like Dave Cloud did to make his EV dragster:
(See thread:
http://ecomodder.com/forum/showthrea...ropped-90.html )
The end result is also a lot of fabrication, comparable weight, frontal area and drag coefficient (with some additional massaging). But all the other car's parts are easier / cheaper to get.
I'm still happy to see an Insight going the EV route! Looking forward to your project.