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

Updatet 31-08-2016:

I got a whole bunch of emails with ideas on the squareness comparator and in the end I found something that I like.
Brian / Toolndie7 on Instagram shared a very nice and simple squareness comparator.

The nice thing about his design is the fact that the fine adjust is close to the indicator
What I also like is the fact that it uses a DTI instead of a normal plunger type indicator, I prefer them for precision measurements.

For the feet of the I am going to follow Tom Liptons idea with the pressed and surface ground balls.

It got mentioned that this type of comparator gives a linear measurement instead of an angular measurements - Thats exactly what I am looking for. When I adjust parts for squareness by machining or scraping I need a linear dimension, and angle does not help very much in that case.