A kind lady donated a couple of her late husband's C330's to our high school photography program. I'm pretty excited to be able to introduce some of my keen senior students to medium format. We have a Beseler 23CII enlarger, but no 6x6 negative tray. If you have one that you no longer use and could donate... or even a 6x7 tray... could you PM me? Thank you!
If you can get that "double black" ( flat black on the inside and outside ) matboard, it works really well. Especially if you cut both sides with a beveled mat cutter.
You can also "tune" it to exactly the size image that your camera makes... I've got a stack of matboard carriers that match my cameras, and I often reach for them even when I do have the right sized beseler carrier.