I have UGF's in all my tanks, except for the 10 gallon cherry shrimp tank. (2 55's. 1 38, 1 29) One 55 has 2 AC 500's, one for each filter plate. The 38 is set up the same way, with an AC 300 running the UG filter. I just put the intakes into the lift tubes. The flow through the gravel is strong enough to keep debris from collecting under the plates, so whatever doesn't get siphoned with PWC's ends up in the sponge blocks. ( 2 sponge blocks in each filter) The filter plates are all Penn-Plax Undertow's, which are a better design than the flat plates.
The other 55 and the 29 are set up with AC powerheads and Quickfilter cartridges. The Quickfilters have bulk filter media wrapped around the plastic cores, and the powerheads are adapted with pvc elbows/vinyl tubing for reverse flow, without using the reverse-flow option on the powerheads themselves. That way, full flow goes into the lift tubes, and keeps debris from working down into the gravel. There is also a layer of bulk filter material between the UGF plate and the gravel bed. Much less gravel, much more surface area for bio-filtration. Thin layer of gravel to siphon, easy to keep clean.