Oh ok, well first off, I forgot you framed it like my tank
I'm such a tard sometimes. Too many projects to keep up with.
What I did is put a hard rubber strip over the Dow 795. Too tired to go find the pic on my thread. In short, I filled the gap with Dow 795 then stuck the hard rubber strip over it. A small bead of Dow 795 was applied to the backside of the acrylic where the hard rubber overlaps. The acrylic was roughed up for extra adhesion.
I'll take a pic tomorrow if you don't understand. The hard rubber was obtained from a rubber supply house and cut to size (1.5" width). The thickness was 3/4" I believe. Enough to be flush with the plywood sheathing.