Well, Michael, I have made enlargements of up to 16x20 from both 120 and 4x5 negatives without a glass carrier and they are quite sharp. Some of them are on display here at our mall at the instruction center. I can understand that some people have preferences, but I seem t be able to get along without glass. We did at EK as well in most cases. They used liquid filled glass carriers for 30x40, but that was more for scratch elimination.
However, this is far from the intended topic in some ways.