Nice progress, However I do have to ask, is the locomotive the only form of power?
I have the Eishindo 'Miniature Railway' set and the same loco struggle with 2 loaded carriages. (Mind you it had the old motor.)
And this is with figures made of soft plastic.
Anyway, you might want to consider adding another loco to the consist just to provide extra power.
Especially if the driver and passengers are made of metal castings.