A couple nights ago I attepted to make my overflow. I was going to do a dual overflow but decided not to because I'm going to do a closed loop. I used c-clamps and a flat bar to hold the plexi to a table at the point I wanted the acrylic to bend. I used a torch to heat the acrylic and slowly applied pressure to curve it into shape.
The problems I had with this - the torch left burn marks on the acrylic. And if you bend it too fast, or without heating it up enough , the plexi will crack. I had a small fracture on one end of the overflow that I filled with epoxy. so no biggy. Anywho, I will probobly just go get more acrylic and see if I can do it better the second time around.
So, I'm going to have a single overflow in the middle, and 2 returns from it hanging over the top of the tank. One on each side of the tank. Then I will set up a closed loop with 2 intakes with strainers, and then have that go into 4 returns that will be drilled through the glass. 2 on each side.
Here is a crude drawing of how it will kind of be layed out.