Use of Magicfalls product

Can anybody advise me on the use of the Pentair Magicfalls? I have two specific questions:

(1) What effect would work best for a short-distance fall (from just under the coping, so only about a 3" or 4" drop)?

(2) I was thinking about using this on one of the return lines from the pump, but in their User's Guide, I see the following: "Use a 20 micron cartridge filter to supply clean, filtered water to the waterfall. Do not use a DE or Sand filter." Does this mean that I shouldn't use the return water from the DE filter? If so, what would one put inline to keep things happy?

Thanks in advance for any info...