I just bought a lightly used Bob Jackson tandem (1980ish) which has Phil Wood discs, in addition to Shimano cantilevers. They are beautifully made and barely worn. Unfortunately, they don't work very well, even after adjusting them. They sure look like they should work better than they do, and given Phil's other products, I cannot imagine he would have put these in production unless they were effective brakes. I've read a little about them online (know about the asbestos issue), but the information is clearly second- or third-hand. Even SB is vague.
Does anyone here have experience with these?