I also use Capt Tolley's Creeping Crack Cure
for all those "good enough" fixes
that Ulladh and I like to make.
I've been meaning to recommend this stuff to Ulladh for awhile, since I think it is a much more permanent fix than Armorall.
But I would check carefully before using Crack Cure to seal around plexiglass to make sure it is compatible. It looks and smells like a waterbased latex formula (either Vinyl acetate like Elmers glue, or possibly PMMA, which would be more UV stable). If it's the latter, its adhesion to plexiglass should be very good, but be careful not to let any excess drool down the window because you may not get it off.