In fairness, I should note here that I know riders who use Silver Bigmouth sidepulls, Tektro Bigmouth sidepulls, and Dia Compe 750 centerpulls on fat tire roadbikes without issue. However, my grip strength is weak and I have damaged nerves in my hands. Braking power with the combination of road levers and long-reach brakes has been an ongoing problem, including on bikes built for cantis. It is useful to know that Paul brakes are an option that works. The Center Mount version of the Racers does not require special braze-ons and can be used on any bike that accepts sidepull brakes, provided there is enough steerer available for a cable hanger.
Paul Racer brakes can be purchased from the manufacturer directly, or ordered via your local bike shop. The company is based in Chico, California, where they have been making parts since 1989.