I like your idea for welding the top of the cage. And as far as the stance goes, it is a race car and I for one would not expect it to sit too low like some of the street cars. Mine will not sit as low as others either because it will be driven on the street on a regular basis and the last thing I want is to worry about speed bumps and pot holes taking out my oil pan or exhaust.
The car is looking great, please keep the info and pictures coming. Thanks for posting.