Actually spoilerons (elevator up ailerons up) kills wing lift. Thats why it helps with an elevator maneuver. A little reflex(spoileron) helps to evenly stall the wingtips so that they dont rock as each wing loses then regains lift in opposite time causing rock. I have a spoileron setup on my spring loaded trainer switch as well. As has been mentioned you can get into some serious trouble if you get real low in an elevator and try to fly with spoilerons engaged. Its really nice to just let go of the trainer/snap switch and forget about it. Truth is however, the better I get I have found I dont need spoilerons, if you make preimptive aileron control moves and dont wait till the wing drops and then react you can pretty much stop the rocking altogether. Takes hours and hours and hours of practice on the sim and with your real plane to get it, especially on a big scale Edge 540 that tends to wingrock a lot.

To get a good waterfall you really need massive elevator deflection, probably at least 60 degrees. Spoilerons help but to really get a true waterfall, that is basically a zero radius rotation around the wingtube, you need that huge elevator deflection. A tight radius loop is not a waterfall.

To really get a mental picture of what a waterfall is suposed to look like, imagine a rod that extends from wingtip to wingtip right through the CG, like a pig roasting on a spit over an open fire, except stabbed through the left side and out the right side instead of in the mouth and out the poop chute, lol. Now grab the plane by the nose or tail and let it spin nose over tail on the imaginary rod and thats what a waterfall should look like. It is not a tight loop, its actually pivoting right on the cg. Do it right and it will get going so fast you will think the wings are going to come off. Its a very cool maneuver.
Also to initiate a waterfall you have to pulse the throttle, full throttle over the top, completely out as its inverted and the full throttle as it pulls into the vertical and back over the top, however once it gets going you leave full throttle and hang on. It will fall like a stone and probably be making 40-50RPMs. A good waterfall can get REALLY fast and can exert some SERIOUS strain on the airframe but man it looks cool. Like like to get it into a waterfall and the let it fall over on its side into a knife edge spin with a little aileron and rudder input.