Thanks, Jay....... yes, I am talking about one of those seatpost clamp racks, except this one has pannier supports on both sides. I have one of these racks laying around so I thought I can utilize them by adding some bottom support. My initial inclination was to use those P clamps on the stays and cut a couple strips of 1/8" thick aluminum and use them as tie brackets. I also like your idea of using canti bosses as support points. I will explore this further. Thanks...