the most important thing in drilling a tank is keep water running over your bit and do not put pressure on the drill. other that that its pretty simple. as for the sump, i don't care much for the silicone. I have used it in the past and had baffles come loose. I have switched to using windshield urethane. same stuff that hold your windshield in your car. its about $15 a tube and can be purchased at any local parts house ( car quest, oreillys, or almost any car parts store) this stuff does not come loose.