I used a red with the ET 15mm base and my sachtler video 30, and it worked like a charm. I know the 20 has a narrower top, but I've used Arri dovetails on them in the past so you should be just fine. Don't forget to order a dovetail for the ET base if you don't already have one.
some pics: http://www.flickr.com/photos/freedom...7603959502677/



