That's basically what I did to get the measurements above, except I used a laser to project the points onto the floor.

I think I've decided that I'm just going to bolt in the subframe connectors and add a couple of stitch welds that I can grind out later, so I can get it on the dyno, get it tuned, and enjoy it this summer. This winter I'll take off all the front panels, adjust the subframe and get all my panels on and aligned to my standards.