Not fully understanding what you're trying to do, so don't laugh if this is way off base, but could you cut or drill out a channel in the wood that you could slide the acrylic sheet down into?
Barring that, I'd prolly try good ole' super glue gel (it's not just for frags anymore! )
Well basicly what I did, Since this corner tank is was going to set on an existing end table built out of 2/4s and I really did not want to drill the table.
I took 1/2 thick compressed laminar wood and cut an arch from one corner that came out 3 inches further than the front of the corner tank. I made two of these and put 2/4 sides and slats to create a riser 5 inches tall.
Now I have an open arch 3 inches from the front of our tank. I have glued a 8 inch strip of black acrylic on the sides and need to do the same along the curved surface of the front. We will then use pond liner to make a beach in front of the glass at about the same level the sand bed will be in the tank. Our hope is to create a continual sand line from the tank through the glass and inot the 3 inch channel. we will decorate the little beach in front with shells our bird tracks or something not sure yet.
When we get it all together we will have pics. in the meantime the tank without the riser can be seen at www.jonezing.com under sea horese tank.
)