the problem with PDTs and Stanton Drives is that they don't have a lot of speed, and they can't be stressed out. Due to the nature of the gearing and wheel diameter, the speed get slower as you use smaller wheels prototypical on MU cars (though the Metroliner runs on 36" wheels, not 33" like other MU cars).
These drives are pretty strong, so they will pull if you put the weight on them, but if you put to much weight, the gears will literally chew through themselves. If you're going to push the limits of the drives, opt for brass gears and not the "standard" plastic gears (it doesn't cost anything extra).
for example, the stanton drive can push about three cars (IHP Silverliner III kits in my experiments), but doing so will wear it down (and it won't go very fast). I stick to a pair, but it would probably be best if each car drove itself.
There is a drive called the "black beetle" that is made in Australia, these are a little more powerful (but also take up more room), and faster, but they are hard to come by.
Elite Juice Jack Modeler.