Well the rear brake should help but remember that about 70% of braking is done by the front brake. Not sure if you want to go to the expense of adding a front disc brake, but that would be the idea solution.
Interesting, was not aware. I almost never use the front brake since I thought it was a sure way to fly over the handlebars. There's no way to attach a disc to the front wheel without replacing the wheel.
Yes I understand the issues with converting a non disc bike to disc brakes. To do it right you would need to change the forks and front wheel hub at the minimum. That is the very reason I gave up on adding e-power to my perfectly fine Trek 7200.
With that adapter I would put the caliper above the disk and add a brace to secure it. The force on the bracket will open the slot allowing it to spin with the disk. I have the same one on me stingray.
please check out pedal chopper.com. he has everything you need. these bikes are designed for 40 pound kids to do 12 mph on. at 6'3 260 lbs i learned that real quick. from bent seat posts to give you more room, kits to change wheel size and choices of disc or drum brakes this man specializes in occ schwinn stingrays and spoilers
