rear brake conversion

I have always considered shortening the rear brake arm 1/2"- 1". The brake is plenty powerful, my ham footed braking would be more controlled. Disc brakes in back are there to save weight. A backing plate, shoes, drum and large diameter hub weigh much more than a small drive hub, rotor and caliper. What races on Sunday sells on Monday.
My Motorcycle endorsement has been on my driver's license since April, 1976.