Installing 3rd Window Trim? Help!

[Driver8]

Okay, I've searched the archives and dug around enough to find, well, nothing. Or at least, nothing specifically applicable to what I am trying to do.

Background: When I picked up my X last month, the passenger side rear glass (3rd window between the C & D pillars) was missing its Shadowline trim. I ordered the piece and picked it up Saturday.

Problem: How does it attach? It has several tabs that align with matching slots on the window frame. There is a mastic-type material or adhesive applied near each slot. When I insert the tabs into the slots, it seems to fit, but there is nothing to hold it in place save the mastic, which doesn't seem to do a very good job. It doesn't remain tightly in place. Surely there's more to hold it all in place than the mastic! The tabs themselves appear to be cut on the ends...are these bent with a special tool after being inserted to hold the trim piece in place? I'm at a loss, and I'm sure that someone has had to contend with this at some point. Any help is appreciated.

Thanks - Mike