Neal, I have an Omega DII with a Super Chromega D head and use both new and old carriers. From what I have been told, the only thing about the new holders is that they have a small frame around the bottom as well as the two notches in the back to set them in place when inserted into the enlarger head. When the framed part drops into place you know it's in properly - although I've never had any problems with the old style sandwich type. You could also check with the people at KHB Photografix to be sure. Their site is www.khbphotografix.com
Hope this helps. I also ended up with a few carriers for formats I've never seen when I bought the enlarger. One looks like 4x4 square and another like half 35mm.