It's a race car - you could bond it in with contact cement if you wanted (although I still wouldn't advise it!), as I presume you're also caged up? Plenty of race cars don't even bond the windscreens in - they just seat and tab them, so as to make them quick and easy to change when they get damaged (for example, rally cars need quick turn arounds - who wants to wait an hour for the glue to dry before being able to get back out on the stage?)

As for the trims - they are purely there for aesthetics. The outer trim does provide a little bit of protection for the glue, by shielding it, but it's not water tight - hence why screens delam and apertures rust (and in a way, trims contribute to rusting apertures, by trapping water and retaining it). You could take both trims off a Sierra and it wouldn't make the slightest difference, other than looks. Exactly the same as my Lexus - I could fit the screen without the trim and while it'd look shit, it would make bugger all difference to the screen or fitment.