Wayne ... the Scanner is pretty consistent in terms of the CG from plane to plane. I fly mine with the CG about 1/4"-1/2" behind the spar. I did not really calculate how far it is from the LE. I can't help you now as I just crashed mine on Saturday. I think you are right about it being 3". When I flew mine with some weight up front and the inverted flight was not as nice. I added no more than 2 oz with the TT46.

Why not try this ... get the CG at 3" level and then add about 1oz to the nose. If you are happy with that you can start to remove bits off later on. With that set up I highly doubt that the plane will be too tail heavy to fly. Try it and let me know.