Ok, we’re down to pretty much wiring 
For those of you running boards that are capable of 128 microstepping, what are you running at on each axis? It seems like overkill for the extruders and Z axis… If you are running at 128 on all axes, have you encountered any issues? I’ve got the radds board with the raps128 drivers.
I agree, anything more than 32x on extruder or Z is overkill. Extruder already has a gear-reduced stepper, and Z has pulley reduction.
Calculate your microstep/second rate at 1/128 for your desired drivetrain and speeds, and you’ll probably find that you’re way over the step pulse generation frequency limits for your controller. As a starting point, I would try to stay below 80khz for 32bit boards or 40 khz for 8bit boards, although there’s some firmware-specific stuff in there to worry about such as double/quad/octo-pulsing the steppers to make up for high step frequencies.
For a point of reference, I run 1/32 stepping with THB6128 drivers on 0.9 degree steppers with a RADDS/Due.
Thanks Ryan, I’ve been playing a bit with your stepper simulator too… Nice bit of work there, thanks for putting it out!