Eheim plumbed to overflow

I have 90 gal tank that i used for a reef tank prior to making the switch to freshwater planted. I have to admit, I loved the reef tank, but a freshwater planted tank is going to be much more rewarding. Anyway, my question is if anyone has ever used a Eheim canister filter attached to an overflow. The tank has two drilled holes in the overflow which I have sealed up with two bulkheads. I was thinking about removing them and attaching the Eheim to the bulkheads. I would keep the water level high in the overflow so there is not aggitation. Water would be drawn down into the canister just as it is now. Has anyone tried this? I thought this would be a great place to hide heaters and plumbing. I can drain the overflow to work on this project without removing water from the tank.