When printing 4x5 it's the enlarger in use that dictates the negative carriers you have to use. That being said, let me try and provide some information that might be useful.
I use the Omega/LPL 4500 II enlarger with their VCCE II (Variable Contrast Constant Exposure) enlarger light source. This light source is of a dichroic design using a halogen bulb, and thus creates some heat at the negative stage. For this reason I find it essential to use a glass carrier. While I love the flatness of the negative and the fact that it will not "pop" in the carrier, I hate the four extra surfaces, which can collect dust. It's just something you live with, the necessity of careful dusting—and often redusting—of the negative and carrier glass.
One thing that I have done to all of my negative carriers—regardless of type—over the past thirty years is to have the negative carrier milled out to allow for full frame printing. It is unbelievable to me that enlarger manufacturers necessitate you crop your photographs when printing in their negative carriers. I will make all of the cropping decisions on my images myself, thank you very much! To have the negative carriers enlarged I have generally had a machine shop do the work by giving them a sample negative, and asking for 1mm of clear film around the image area. Whether a glass carrier or glassless, this will allow the negative carrier sufficient area to grip the negative and hold it securely in place. Some of the carriers I have filed out by hand. On a larger negative carrier, such as 4x5", this had to be done carefully, so that you don't enlarge the opening too much and allow the negative to fall through. In addition, I like to bevel the edges of the negative carrier toward the negative itself to minimize any shadowing or reflections the carrier might cause. After enlarging the negative carrier I paint it with flat black paint, and off I go to make prints.
Posted by: JOHN SEXTON