Collecting ideas for a squareness squareness comparator

In the recent time I find it more and more difficult to measure squareness to a high degree of precision - The Starrett surface gage just is not sensitive enough when I use the ball end of the rod to contact the work.

I saw Tom Liptons great squareness comparator which is a beautyfull design and decided that I wanted to build something in that line too, but with my own twist.

Tom Lipton squareness comparator Part 1
Tom Lipton squareness comparator Part 2
Tom Lipton squareness comparator Part 3
Tom Lipton squareness comparator Part 4