yes you need to cut the corners so it will fit flush with the tank. all the over flows that i build have teeth at one inch. the water comes up about 1/2 inch on the teeth. in your case you should have the overflow about 1 inch under the center plate [ center surport] that way the 1/2 inch over the dam will clear the center plate and still not have a water line on the outside of the tank. hope that helps some. dan
350 gal. 7\'x36\'\'x25\'\'tall, , 3-400w.mh-10k, 2-6\' vho actinic, 175gal.sump, 6ft. 100gal zenia fuge,calcium reactor, kalk reactor and a carbon reactor. 7\' turbofloter 5000 skimmer.