Currently we have caliper brakes with an Arai drum. Love the drum/drag break for long descent, especially with panniers. If we upgrade to a "modern" tandem in the near future, I like the idea of disc brake stopping power because I have sketchy stopping power with the calipers right now. But with disc brakes, is there still a heat build-up issue on steep descents, especially with loaded panniers? Anyone with disc brakes use a drag as well?