got an older school RD 3 on a mag 9.5 with some added bioballs. does just fine. few points at least with mine that are helpful to work with.
1. shut the skimmer off while feeding, rearranging the tank, hangds in the tank dosing addatives etc etc. the surface tension is broken by the oils in your hands and in supplements so the skimmer slows or shuts down for a bit (1 hour or less usually) but if you cut the skimmer off then turn it back on once your done or the feeding is, it works without pause.
2. the gate valve adjustment is FINE very FINE. a little change can illict a very large swing. its best to run it wide open at first to break it in, then set the water level at the base of the large tube
( sometimes closing off the air inlet helps a bit to get it started but when you cap off the air the water level rises a bit, so you may need to still fine tune it) once you start tuning it and think you have it right, leave it for an hour or so and come back. the skimmer takes a few minutes to really settle in to the new level and begin producing. if your level isnt right that is where most flooding incidents come from.
3. cleaning the neck can be difficult, i use an old crest spin brush thats battery operated while the skimmer is running to pull gunk off the walls and it gets into the cup. otherwise whiping it down is great. just dont wash the skimmer itself or you ruin the efficiency until it rebreaks in.
other than these tweaks and or issues, its a model skimmer, its no more work than a needlewheel really once its broken in, and as a side benefit the sheer amount of air being added to the water saturates your oxygen requirements for the tank. also good for effluent from reactors etc to blow off the CO2 in the water.
take it slow and steady and youll be a very happy aquarist.