The OP is talking about a kit too and not the GP ARF. I have set up a couple of the GPs and they are a very light plane, with the OS 1.20 they both still needed nose weight. The Super Stearman I set up used the pumper so there was a tad of extra weight there already. A trick I used to do when I was still building Bipes was to make the fuse nose section longer then mount the engine on the fire wall. The fire wall was the last thing I mounted while the plane was still in the bones but the controls were installed, I would just pin the fire wall in and move it around until I found the spot where the plane CGed. Then mount the fire wall there and cut away the unused section of the front of the fuse. It isn't true scale but it kept the lead out!!