I suggest contacting the owner of Focal Point Glass. Its business in Deltona, Florida specializing in machining carrier glass in both regular slide glass and anti-Newton glass.
He will know exactly the thickness, length, width, and what beveling might be required to fit your Durst carrier.
Would have thought it would be the same thickness as the Femomasks (3.04mm). Measuring my FEMOGLA, it comes out at 2.86mm - Nominally, 3mm thick glass should do the job
also, say I want to use the glass on top and the mask on the bottom. my bottom mask (as I think every Femomask) has film positioning pins. I guess those would hit the glass on the top - unless I create pin holes in the glass as the ones on the top Femomask.
so, should I just take the top mask and put it on the bottom position?
Same shape and size as a Femomask, but only two edges have a 45 degree bevel on them. One would normally use a plain glass FEMOGLA on the bottom and an A.N. FEMOGLA on the top - More surfaces to keep clean
Only one half of the Femomask pair has locating pins (except the 5x4 mask) - You could always use the other half or cut one from a scrap of mount board.