Got into the "hanger" and banged solid rivets again today. I may have reached a milestone as I drove six without incident. Meticulous measurement of rivet length and moving the arbor press to the concrete floor and off the workbench proved to work. Also rotating the piece 180 dg if sideways bending of the rivet began worked to get a usable result. Another 20 practice at least and I will try a few on the spar.