I haven't been following the sprag clutch (freewheel) discussion, but I thought I'd mention a company I came across years ago. They make a one-way clutch that carries an astounding amount of torque for its size. A quick look at their website suggests they concentrate on replacements for specific applications like auto trans parts and racing torque converters, but a call might turn up a solution for what you guys have in mind.
http://www.epilogics.com/md/index.htm Chris
