I like that, also gives you graduated spots for lining things up. I personally used my machine to drill 1/4” holes in X and Y, then I use 3/4” long 1/4” steel dowels to line up along either X or Y (or both with two pins in X and one in Y). Charlie at Triquetra CNC also has a short video of doing something similar to yours with a regular sheet metal square. Lots of ways to skin that cat, always like seeing how other folks do it, there’s always gonna be a time when my way doesn’t work, good to see other options.
Thanks for sharing!
Dan