The mk 11 now has tracks, suspension and appears to all be running fine. I have tested it driving over rough ground (a carpet floor covered in Lego) and it did not seem to stall or slip. The gear box was running perfectly smooth and has not shaken itself to bits in the initial testing phase. The tracks are a slight section loose but removing a rung leaves them far far to tight so will add a couple rollers on the top to add a small amount of extra tension. Turning seems fine and the drive system is complete. I am not going to build up the central body before making a new turret. The mk 10 had the moving shooting turret from the mk 9 model. This was not scaled correctl for the body and was another reason for the over weight on the mk 10 which caused the drive systems to fail. Hopefully the new gear box will allow a drive with full weight.