I also vote for drill your tank. I did this on one tank and it is the way to go.
I also have a CPR Style (which I am going to get rid of and drill the tank). It works well and I have had no floods with it. It depends on high flow rates to keep the air bubbles out. I have lower flow rates, and you have to watch it. About once a week I have to break the siphon and restart it (which is real easy) in order to keep it flowing properly. The suction from the venturi on a powerhead was not strong enough to keep it free of air bubbles. I now have a vacuum pump on it which solved the problem. Here is a link to one of these vacuum pumps.
http://www.marinedepot.com/md_viewIt...dproduct=KTALP
It is also hard to clean. It is black so it doesn't grow algae to quick but when you do have to clean it, it is a pain. The siphon section is removable but you can't get a brush around the square corners of the U so you cant clean a section of it properly. In order to clean it I have to shut down my sump for mabey 6 hours, fill the U with bleach in the sink and let it soak, then blast it with a water hose to clean out the dead algae. Thankfully I only have to do it mabey once a year.
The CPR style works well and I am fairly happy with it but best of all is a drilled tank. My current and any future tanks will be drilled.