Hard to day what happens over in China. I just stuck both of my command equipped ones on two loops and went to full throttle, they both had similar top end speed as the video I previously posted. I don't recall ever having any of the half dozen or so I've tinkered with have a slow running issue. I also have chassis pieces, extra wheels, etc. I actually have removed the traction tire from my command versions so they have better outside track contact, with only one wheel touching, going through many switches is iffy with the traction tire. These were never designed to pull a big load anyway.
If I do a dual-headed configuration, I can keep the traction tires and run all for of the little motors off one motor control, that should give them more pulling power. 
