After I motorized my trike, I determined that the disc brakes that came with it were not really sufficient. I changed to Avid 7's (mechanical). I am still not satsfied. Perhaps hydraulics, with a split so it operates off one handle would give me the stopping power I would feel comfortable with. As you build, please let us know how the brake system you use works.
Thanks
Van
(I may not post often, but I'm watching)