Kernow exchanged mine for one with the body removed. Pipes cut etc. Some minor damage to the pipes.
I filled a length of brass tube with white metal. Machined to 14.5mm diameter and then sliced it into 7mm sections. These then drop into the smokebox from underneath and slide back into the boiler. This made the total weight 194grms. The loco could then pull 3 coaches up a 1/30 gradient without problem, except the motor in my opinion is to small and more suitable for N gauge. Running with a Zimo decoder (suitable for coreless) in the bunker the loco would slow for no reason. The loco would stall on the gradient with the motor still powered but not enough power to turn the wheels even on full power.
As I was now getting a bit fed up with all the hassle I changed the motor for a convential motor. I had to make a new mount and remove a small amount of metal from the weight over the motor. But I now have a loco that performs as good as it looks. I just need to repair some of the pipe work.
I would like to point out that is only my opinion on the motor, mine could have been faulty.