[RHD]

I never trim the long cork seal. Seat it at both ends and fit the pan watching the gasket does not slip from either side of the seal while compressing with the pan. (Easier said than done). It will compress and when fitted properly they very seldom leak. I have used this method for 49 years with good results.This suggestion was told to me by a Model 'A' mechanic of the day. He died some 35 years ago and he told me the cork seals were made that length for a purpose. He said that Ford never gave anything away. Use a good (expensive) gasket cement. Never use RTV.
Re tighten pan bolts after a short time.