backdrive value for overriding Victor dynamic brake

[DonRotolo]

Technically, "Backdriving" means you are providing voltage to the motor in the opposite polarity to the direction the motor is turning. You're not doing that.

The brake in a Victor turns on a combination of FETs such that the motor sees a short circuit (or very nearly so). This causes the motor to be a generator, turning mechanical power into electrical power; it is this conversion slowing the motor.

What you're doing is just fine for speeding up the motor a little. The ideal value depends on your mechanical setup; try different values until you get what you want.

An alternative would be to run without brakes, and really backdrive the motor to slow it down as it gets close to the stopping point.