A few weeks ago I set about making a styrene insert for my Stargate model. After several attempts and some advice from guys on TMP I finally have a finished product. I ended up using 4 Pieces of blue water effects styrene from Plastruct and one sheet of plain white styrene. I made the insert look the same from both sides so, starting from the front I have a layer of wavy blue water, a layer of bubbly blue water, the layer of white, a layer of bubbly blue water and then a layer of wavy blue water. This gave me a depth that looks really nice and the appropriate blue color I wanted.
The most difficult part of the process was gluing the layers together without causing any hazing or dis-coloring of the water effects plastic. This was ultimately accomplished with Model Masters Airplane Canopy Cement around the edges. It worked exactly as I wanted and caused absolutely no discoloration. I then ran a bead of clear RTV silicone around the edge to hold it in place inside the gate when it was popped in. I originally intended to use magnets but this proved nearly impossible and good old friction ended up being the better choice.
Now I just have to make a dial home device of somekind and I'll be set.