Just got off the phone with Felpro tech support. They told me that the 360 rear main seal was designed to be used as supplied with no trimming. This is part# BS 40651.
I have been researching this a lot and have found no evidence of anyone trimming this particular seal. It is designed with the metal ring slightly below the surface of the seal half ends to allow for the Viton to compress slightly when put together. I could not figure out a way to duplicate this after trimming, so I kept searching for more info. According to felpro, the seal is designed to protrude .060 inches or more prior to assembly.
