The next phase was about a year ago, when I started thinking about using a 2006 or newer Miata chassis. The problem is the wheelbase is about 3.7" shorter than a 510. So I did a photoshop to see how that would look.
I did a mild chop top, shortened the back door and front fender, and removed the rocker panels:
This is how tall the roof looked before the chop top photoshop:
