oy vey...........
First I only had a drill bit one size too small.
then I found an extra box of bits in the bottom of my old tool box. One was the right size but turned out to be a wood bit.
The next morning I grumpily reattached my old sp sidepull to go get breakfast, and - in a moment of mad desperation, after reading every repair manual I had one more time, I actually centered the old brake!!
Now why couldn't I have just figured it out
before I drilled?
I guess I was motivated by hunger.....or maybe my mech skills improve when I'm not awake yet.
The brake seems a bit more flexy than before but still stops fine. I will eventually pick up an 8mm steel bit and slap on the DP caliper. But nice to know my brake is finally centered....