"Nonetheless, the new brakes are mounted (though I had to drill out the holes to fit what I previously considered to be standard mounting hardware, but which the cheap-o generic calipers did not use)"
Whole-heartedly agree the cheap-o calipers must be replaced! Looking to do the same on a Mercier SC1 I just purchased. Would you suggest ordering a different set/size Tektro brakes, so I wouldn't need to drill out the holes? Or should I follow your lead?