If you want a self-energizing front brake, it will have to be not a SunTour but one of the original Scott-Pedersen model. Of course, some have expressed concern about the possibility of locking up the front wheel. A self-energizing rear brake used on the front would be self-deenergiziing, with the rim driving the shoes outward instead of inward. I would think that stopping would be all but impossible.
My second tandem ride with the SunTour SE rear brake was as good as the first, with lots of fast descents kept well under control.
