Okay Mark, I timed yours on my 2-800MHz PIII, 1GB Ram, ACAD 2002 w/ 10,000 circles w/ original radii of 0.8154. I'm not creating one this time. Here's your test score.
changed to 0.15
Timed CHGCIR: 3.281012
changed code to set radii to 2.0
Timed CHGCIR: 3.359024
from 2.0 back to 0.15
Timed CHGCIR: 3.311992
Stig, I'll test your's on the same set w/ the same parameters when you're ready.