Re: low weight vs low drag.
Ive built 3 vehicles so far from scratch, and have learned many things from lots and lots of mistakes :-)
There are some "middle paths" that can be taken, like the use of a pre engineered front end, common on ebay most of them follow the design of the ford mustang, just search "mustang ifs"
also, personally, I am a fan of the reverse trike, better aero, lighter and a whole lot easier to register.
there is an active community of scratch builders over at locostusa.com for the not faint of heart as well ;-)