2-17 is correct. They will 'seat' themselves as running time is established.
PLEASE NOTE!!! If you are going to run the old trains (pre-war), take the time to run a bead of epoxy around the back side of the copper commutator where it butts up against the wiring. It is especially critical on horizontal commutators such as the # 33, 38, 42, 53 etc. This will save you agonizing over paying $50 - $75 to have the armature repaired due to a segment coming loose and getting ripped off by the brush. Harry