Any of you that are looking to buy or build internal overflow boxes here is a suggestion which I will take pictures of shortly.
I decided to have some custom made internal overflow boxes built out of 1/4" black acrylic plastic. I drew up a design and sent it out to three plastic fabricators, only one responded with a quote for get this....364 bucks plus taxes for two 4" X 8" X 30" high boxes. Of course that inlcuded the labour to bend them into a three sided box as well as cut the water flow "teeth" across the top....So I got to thinking and this is what I have come up with.
I bought a 36" long piece (shortest I was permitted to buy) of white PVC pipe, 8" in diameter, 1/4" side wall thickness. I cut it in half lengthwise, in essence giving me two pieces 36" long with a 4" radius. I then cut them to the final height I need them. I then drilled 3/8" holes across the top and cut them out using my dremel tool essentially creating "ports" for the water to flow through. The 3/8" holes were spaced 3/8" apart. I then painted it black to blend into the back of my tank. I then siliconed them into place and viola, internal overflow boxes for a grand total of $17.20 for the pipe, $6.79 for the plastic spray paint and 3 bucks for the tube or silicone....a long way from 364 bucks and they are round not square so they blend into the back of the tank even better. Will post pictures shortly!