there was a thread on sloppy borders just a while ago. I will repeat what I said there...I suggest that you think long and hard before you destroy an otherwise perfectly good neg carrier. Perhaps, you can make a suitable neg carrier out of matt board or something? We all need to be careful about "modifying" gear that is (generally speaking) not being made anymore.
You could also use the 6x6 with glass to print 35mm and get everything you want and more!
Do not remove the glass. Usually this leaves the neg unsupported.