I wanted to run a longer train than either of my engines could pull so I tried running them together. On their own my Kato SD40-2 runs faster than my Atlas GP30. However, when I run them together they seem to work fine (no bumping or coming uncoupled) and can pull all of my cars. They are run on traditional power with the faster Kato in front. My question is whether or not it is hurting either of the engines running them attached when they normally would be at different speeds? Any opinions would be greatly appreciated.