Do you still have your glass carriers made from filter glass? if so, nothing beats a an A/B comparison. I certainly never noticed any difference in image quality between prints made with glass carriers and without glass carries, except for the obvious improvement in sharpness toward the edges. I have had trouble with Newton's Rings on occasion. But the lab where I worked always had a 4 x 5 carrier with anti Newton Ring glass, that I could use.
At one time Beseler made a 4 x 5 negative carrier for film pack film, which had the thickness of role film and had the tendency to sag in the middle. The carrier didn't open. Instead it had a sunken area where the film was placed and it had grips that would grab the film and stretch it tight when the a lever was moved. It worked well on standard 4 x 5 sheet film too. No need for glass.