Hi John:
For the CG, there is a jog in the wing three ins. out from the fuse. At that point CG is two ins. back from the leading edge. I was using 1800 MA seven cell nicads and getting about four to five mins. of fun run time
I did a couple of things to improve the performance from stock. Ducted fans need a close fit at the blade to duct gap. I put thick CA on the outer edge of the blades and filed them down for a close fit. Probably 5 to 10 thou. gap. as they will stretch when wound up. I carved the blunt trailing edge at the air outlet of the fuse to a long sharper, tapered edge. The air inlets should be well rounded and smoothed. After you launch it, give it a chance to build up speed, as the faster it goes, the more air is rammed into the front and the more efficient it is and builds up more speed. Make the turns big to keep the speed up. Hope this helps a bit. Any more questions, just holler. I would like to get the one in the box up and running with a brushless motor and lipos. Should be a big performance jump with more poop and lighter.