Okay, let me get this straight....you have a simplicity plus system right? That means the back 4 inches of the tank was designed to house a wet dry system, correct? If this is the case, (as was the case with my Tenecor 85 gal simplicity plus system that I purchases used), then you can drill the tank with water in the main display. I drilled my tank when it was empty, therefore it was alot easier. Drilling with water in the main display will be a challenge but I think it can be done. 1) My simplicity plus had two return holes on that internal wall that I plugged, since I ran 3/4 inch pvc returns in the converted overflow area and back into the tank, 2) once the return holes are plugged this would allow you to lower the water in the display tank down past the overflow cutouts, 3) now you have water in the main display without refilling the back 4" area, (which in effect will now become a giant overflow), 4) drain this back area, 5) you now can drill your holes without worrying about the main display. Here is a possible problem: you need to drill not only the tank but the stand that the tank sits on. I intitially cut a rectangular hole in the stand top to accomadate both the drain and return holes, (and associated bulkhead nuts), but since you are keeping the tank filled you won't be able to accomplish this. My bulkhead seats up to the tank not the stand. By not removing the tank from the stand you will need to drill through both at the same time and seat the bulk head fitting on the inside of the stand. I'm not sure if you would develop a leak in between the 2 layers of acrylic. Any thoughts by other reefers?
Frank
Frank