Try the Zinger Pro. I gained substantial rpms over the standard Zinger. This was on a plane I have with a G-62. I havent run my 4.2 yet. My fuse still isnt glued together yet.

I wouldnt worry too much about chasing that 6000 rpm mark though. If youre at 5600 on the ground I bet youre over 6000 during an actual flight. I bet youre getting good thurst. Also .. maybe the 6000 figure on the spec sheet was with that flimsy but scale 3 bladed prop.

chuck