Jim,
Greetings. If I remember correctly, i trimmed after gluing in those areas. If you scroll back up to post #1 and look closely at the pix, you can see exactly how much extra material I had while gluing. It appears to be an inch or so at the front and forward of the B pillars.

Good luck with the project..........................Heat, stretch, clip, heat stretch, clip

regards,
Al

Jim, don't trim until after it is all glued and set.

lookin good. if you put the headliner in a pillow case and throw it in the dryer for a while, the wrinkles go away.

If this helps, my headliner install starts on page 17. I trimmed after it was set.

http://forums.pelicanparts.com/porsche-911-technical-forum/626050-saving-73-crusher-17.html