You might check out Darlene Zimmermans, TRI Tool and the Recs Tool
I got this info from Bonnie Hunter. Tried it the other day for the first time and it worked!
The 2 rulers that I have go from 1" to 6".
Hope this helps. Not sure of the name of your inverted diamond square.
http://softexpressions.com/software/...zQuilt.php#tri scroll down to tri recs tools