John Cutler
Hi Dave
The M7 was one of my early RTR conversions and is fairly straightforward; I have done 2. Both suffer from wobbly driving wheels and are due to return to Works to correct! This might also partly explain why they are not particularly good runners compared to others. The possible pitfalls are the pick-ups; wobbly wheels do not help! On mine I think I did not bend them out enough to be in constant contact with the drivers; at least one M7 seems to rely predominantly on pick-up from the bogie! In hindsight I am not sure I agree with the recommendation in the Manual Sheet to allow a lot of sideplay. That undoubtedly exacerbates the pick-up issue. However, I found that the M7 does not like A4 turnouts at all and complains at A5s. Maybe the answer is to allow slack in the sideplay but fit new pick-ups?
I hope this helps.
Good Luck!