I have been in touch with Bill Maxwell. He makes probably the best groundglass on the market today, and you find a lot of comments about this glass on the forum if you search. I would love to order his glass as a squared corners variant for my 8x10", but we need some more folks to join to get the prices down, since this is a special order. I feel the squared corners gives me more control than the cut out variant, and I know there are more people like me.
Here 's the prices I got from Bill Maxwell:
"If I special order just one fresnel from the people who do molding for me to my specifications (which results in the very high quality of my HI-LUX 10.5 Fresnel), I have to pay a set-up fee which would make the first fresnel about $620.00 (I typically order as many as 100 pieces to get a reasonable price per piece). If I order two or more of these fresnels with square corners, then the price per fresnel goes down as the set-up fee is diluted. Two HI-LUX 10.5 Fresnels with square corners would be $430.00 each. Three would be $368.50 each. Four would be $347.50 each."
Please comment if your interested!