Range is 1.79 -05 to 1.49 -06 on the plop analysis. Only slightly better with the 54pt and the 27pt had a odd pattern with about the same readings.
Nice. I guess the quartz makes a bit of a difference as it has a higher Young's modulus. I am used to seeing mirrors over 28" with a 27 point support, so I was just curious how the 18 point did in PLOP. You have a heck of a great optic there.