I have a GX 4 and the difference between it and the G 4 is only the pump, if that helps.
Also the closer you have your pump inlet to the water surface the better it will skim. (collect more proteins and such that float on the water surface) So you could make a elbow up joint.
Dave
this is a good skimmer prodution thread on Reef Central...long read but good
http://www.reefcentral.com/forums/sh...hreadid=554786