I've made one of those diy pvc overflows for my 10g before I took that tank down. I never used it because the pvc I used was too small, and couldn't keep up w/ the pump I was going to use, and when I remade it with bigger pipes, the siphon wouldn't keep. But the first one worked great in trial runs :) Siphon never once broke when I would turn off the pump. It would stay filled, but stop siphoning, ready for whenever I turned the pump back on. My problem with it is not enough surface area, but I'm sure it's easily redesigned.
I'd love to see pics of yours, too, solar. The pics I kept finding on the web aren't of all angles, so I know I was off in something when I made the 2nd one. No air leaks because I sealed it w/ pvc glue. Dunno why my 2nd one wouldn't keep the siphon. I have no plans making another one, but I'm sure others would love to see it.