Why remove the lenses..? Raising it to 13"-14" off the water line would be less work...16" cone plus light width.. Depth f/b is 18" right? Taking the lenses off and move it down to 7-8" Both should be roughly equivalent.. you will get the most depth penetration by moving the light down as is but sacrificing spread f/b in the upper couple of inches or so.. You can check it out w/ the Lux meter.. you only lose PAR buy not doing a height adjustment (mostly spill) Sorry for the confusing mess. It's actually a partial answer to both the old and new questions.. Why? Got a visible dark cone between the 2 lights?.. Another method is to move them closer together and take the lenses of the end ... Increases PAR in the center and decreases it at, usually, less used ends.. black bracing shadowing makes anything a bit more difficult..