The tank is not a rimmed tank. The black trim you see is purely aesthetic, and is presently missing from the left and back sides of the tank. A 3/4" sheet of glass is flushed against the polystyrene, or if I remove it, the wood. The entire inside perimeter of the 3/4" glass bottom has long, 1/2" rectangles that are siliconed to the inside walls and the tank bottom.
Considering this, will the polystyrene really have such a negative effect? I begin work on the sump this weekend, after which the poly will be permanent.
On another note, I have been debating about whether or not I should put the trim back on, or else take the rest off. It is about 1mm thick. Will it's absence on the left and back sides result in an incongruity and failure?