The subway sets have a couple of things working against them:
1: the power truck block is from the RailKing streetcar, so not really engineered for pulling much.
2: the non-powered cars have trucks that basically make them into dummy diesel locomotives, with all the drag that entails. That's probably the biggest factor affecting their pulling ability.
I've been known to run ten-car subway trains (just like the real ones), but I knew early on that I'd have to add a second powered car to make it work in that configuration , and that's how I run them -- with the second unit midway down the train.
---PCJ
