Hi everyone!
First, THANK YOU SO MUCH for all of your advice AND encouragement! We're so grateful we have a place to turn with our questions! I'm feeling less forlorn today (thank goodness!)
We took your advice and lowered the filter by several inches, implanting it in dirt. Doing this also allowed us to bring the liner almost all the way up to the lip of the spillway, too.
(We should probably have pushed it forward some for a good sound and waterfall visual, BUT we had been hemming and hawing about the stream/cascade or full on waterfall effect. We're happy going with the babbling stream effect, given the position of the filter.) Now we're challenged with making that look good and be functional!
I think we should change the shape of the berm by creating shelves where we can easily put rocks, but my co-designer used some concrete in the berm that he says he cannot dig out. (Grrr.) So we're stuck with a slope, which is less steep than before. The trouble now is that if we put rocks climbing up the slope, we get too high!