I'm not sure where you mean to put the white laminate, but if you can actually see it, I don't think it will look very good. I'm kind of against white.
My idea is really just to use small posts on three sides of the tank. Nothing fancy.
20w T5HO? I think the smallest T5 bulb is 24" and the HO version is 24w...? Can you get 18" then being 20w??? Never seen them that small...only T8s.
I can't forget to put a lunar light on my tank...