Hey Fishindude, I am going to be doing the same thing with my 40 breeder. Foam/rock wall over the overflow. What really inspired me/ made me think it was possible was this thread on RC, http://www.reefcentral.com/forums/showthread.php?s=&threadid=1437901&highlight=foam+rock+wall. It looks like this lady had a lot of success with the method she used. I am using the touch n foam pond foam filler, i had to order it online, but it seems like the safest stuff.