Track - uses the chassis frame from the driver axle. Track + uses a PB back of wheel wiper on a PCB board. I wanted pickup on both sides of the chassis, and did not have the old PCB/Wiper assembly that mounts to the chassis where my nylon scree is. Also was going for motor isolation in case I decide to add a decoder.
Right now I am just trying to ensure it runs smoothly, so now I have 8 points of pickup with the tender trucks.
There is an easier way to lower the flanges, and that is by using a flat platen horizontal belt sander with a fine grit, touching the six wheels at a slight angle (less than 10 degrees) to the belt length axis which will grind all six simultaneously while the wheels spin. Just have to be careful not to run too hot leaving it on the belt too long and measuring diameter in between. Obviously, doing this without the motor and cleaning it thoroughly before reassembly is a requirement.