Have you considered using two speed pumps? I have just configured my pool with a similar setup to yours. I have about the same size pool with a 2/0.5 2-speed on the filter and a 1.5/0.33 2-speed on the waterfall/slide. I figure I'll run the pool at low speed through a sand filter almost exclusively. The waterfall will have subtle/sunami selectability with the 2-speed. My pool will be filled at the end of next week. I'll be glad to share how it worked out if you're interested.