O.I.C. .. I thought you were saying he was depending on a front caliper to soley stop the bike .. Double rear brakes makes sence because you're backing up that smaller single piston caliper....

Those pics help to demonstrate why its a good idea to have the caliper float with the wheel and rotor .. notice that only about 1/2 the brake pad is in contact with the sprocket as it gets adjusted back ..

If you use a sport bike 2 or 4 piston rear caliper .. (not a lot bigger than that 750 front caliper) mounted to a bracket that moves with the axle.. You'll have full surface all the time and won't need a secondary brake in the back ..

I've used a GMA brake and pulley setup, that comes with a small 4 piston caliper, on my driver for like 6 or 7 years now .. and that will pull that big sled .. with this big slug on it... to a halt .. and fast .. But you need the proper caliper and full surface to implement that ability .. and that requires the caliper to always stay with the rotor..
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