I've successfully trimmed the ridge off of a regular tri-clamp style gasket on a filter screen too. The right kind of gasket is available from St. Pat's. Made for this application. Avoid radial scratches the go across the sealing surface.
Are you speaking of the silicone gasket? That is the type I have and tried trimming. It seems like it may work on my keg but the flange on Yoopers seems thicker so I cannot get the clamp closed.
The one on the bottom right?
