I didn't use any adhesive on my vinyl roof. I stretched and stapled around the edges. I did quite a bit of testing when I got he vinyl and as long as the the surface is intact it's very waterproof.
I just got the trim installed yesterday. I cut the vinyl back about a quarter of an inch from the edges and sealed with silicone. Once that was dry I put down another bead of sililone and installed the trim.
I spent a lot of time polishing the trim before I installed it.
Hope this helps.
Darren