Try and set the ESC half way between the motor and the battery otherwise you might get timing problems, and don't forget some cooling holes to keep the battery and ESC cool.
On my Mk 1 I ended up with 100g of lead in the nose, Mk2 only needed 30g as I did as you have and moved the EDF unit as far forward as possible and stuck the battiers (2No 4s 5000mAh) in the nose.