My opinion and there are lots of them here, I would put a return spring on the brake lever with a stop. I would not depend on the tiny little spring in the brake cylinder or balance around the lever pivot point as a means to release my brakes. It may not be a DOT requirement as some here like to use as a standard, but it is a personal safety concern for me. Plus hitting bumps on the road is enough to move the rear brake lever up and down. Applying the brakes, the brake light and causing drag on the pads.