Headliner side molding and weather strip channels

I installed an ABS headliner in my '74 Scamp. I'm struggling to mount the trim that runs he full length of the drip rail. The abs seems to add too much thickness for the clip to slide over. Is there a trick to this?

Also, does the stainless weatherstrip channel go in before or after the headliner trim? If anyone has any good pics of these pieces installed I would greatly appreciate it.