Did you put it on all driving axles or just one? In the case of the Black 5 I modified, it only needed 1 traction tire to more than double traction and this had no effect on pickups as that loco had 12 pickup wheels to begin with. Most kettles these days have pickups on tender and/or carrying wheels so putting tires or bullfrog snot on one axle should make no difference to running. And I notice that some of the new 4-4-0 models(T9, 2P etc.) have traction tires on one axle. I have one, very powerful and no loss of smoothness.
Agreed about the 201 Anto, a little underpowered for a model of a 3000hp loco.