link to all three mods
http://www.asmskimmer.com/modifications.htm
finally did the recir and feed mod w/MJ1200 to my G3 last week, can't say a whole major lot of difference from before. Might need to either change feed pump, go direct from one of my two overflows or maybe some fitting inside the skimmer to get the water moving differently.
As for the gate mod, does give little better control, just because turning a knob a lot easier than pulling on a wet slimmy pipe. But even before the gate mod, keeping the water level constant in the skimmer compartment, skimmer production pretty stable.