Durso...Does this look right?

[Aqua Pro Builder]

Brend, with HOB overflow you can definately experience a flood with the pump going off then on. Not sure if theres a fix to that problem.

It's very simple to fix that-2 cups and an u-tube to maintain the siphon when the water drops below the overflow, then when the water is up a again, water will flow back into the overflow and water will siphon from one side of the u-tube to the other then to the drain and sump.

Remember my thread of "sump on top of display"? Everybody thought it won't work due to flooding but that's how I originally solved it. 2 x 2 liter bottles, 2 x 8 oz cups and a bunch of straw. Now, I bought an overflow box with the same design built in and sold it to my friend who has no patience to wait for me to make another one. I'll post a diagram in my thread when I have time to draw.

The pic from herman use the same thoery except that it also has the air hose to drain trapped air in the U.
http://www.manhattanreefs.com/forum/general-discussion/10465-why-cant-someone-make-better-overflow-desings-2.html?highlight=design

 

[Aqua Pro Builder]

Silicone does not need a "rough" surface for bonding.

In fact, I feel silicone works better in smooth surface, kind of like the original AA glue/Crazy glue whcih works better in smooth surface even though the physics behind is not the same.