Thank you all for your replies, in the for what it's worth category, the balance is dead on according to the assembly instructions as was the amount of engine down thrust. I have reduced the down thrust to 0 relative to the wing incidence and that did help VERY slightly.
I'm still unsure of which way to go with the CG, but I think I'll try moving it back a bit, I'd rather err on the nose heavy side than tail heavy, I like 1320Fastback's comment "nose heavy doesn't fly well, tail heavy flys once".
Again thanks for you info, I'll do something even if it's wrong.
Dan