32 rear window question

[kb426]

I took the new rear molding out of the package. It has a round bead and a flat lip attached to it. Am I correct in assuming that the tapered side of the flat lip goes to the outside of the cab and the round bead fits inbetween the back of the cab and the garnish molding? Is there an easy way to form the molding around the corners? Does anyone know the amount of measurement I can subtract from the garnish molding to cut the glass right the first time?
Thank you