IIRC, for the double diaphragm pod you have to cut away the old inner diaphragm then slip the replacement inner diaphragm (with a hole) into place and then fit the outer diaphragm. George gives instructions to do this.

I didn't have luck rebuilding double diaphragm pods. The replacement rubber is less pliant than the original rubber and the vacuum system in my SDL couldn't pull the pods completely shut. Better than nothing but there's a stretch of I-5 through a cattle ranch near Coalinga CA that requires the cabin to be hermetically sealed

Sixto
87 300D