I'd done a similarly-major project on mine with a completely different approach.
I put in an Atlas flywheel in the drive train to smooth the motor out, and taken all the lateral play out of the drivers with shims, and then blinded the second and third axles; that was to get it around 11" curves on some hidden trackage and 13" on the main. Worked very well. Blinding drivers on a brass locomotive is not for the faint of heart, I'm not recommending it, but it did work. I had to do it in the chassis with a file as it's next to impossible to get the thing apart without desoldering something.