I rode a bicycle for a few years with no rear brake (700c rim on a 26" mtb iirc). Obviously most of you stopping power is from the front, but it's not until the rear is missing do you appreciate the stability it adds especially in snow or really slippery conditions.To save weight, remove rear disk, caliper and all hardware associated with rear brake.
It's a v'twin. All the rear braking power is handled by the two chunky pistons trying to slow down off of the limiter.