The start of any true road race car begins with stripping and stitch welding the unibody after the cage is built. If you try to stitch weld before the cage move around alot and don't try to finish one area too quickly. Weld a few one inch seams and then move to another area of the car. Very time consuming and you should use a mig welder to do this. Using a tig to stitch a car is a pain in the ass, I won't do it again. Also a chassis rotisserie helps alot.