I'm doing something backwards here. Or at least the results are backwards. Here's my math:
Mic source point A = sample #17,835,732
Mic source point B = sample #189,621,177
Span = 171,785,445 samples
SBD source point A = sample #15,387,235
SBD source point B = sample #187,171,636
Span = 171,784,401 samples
Mic source therefore spans 1,044 more samples and needs to shrink to match the SBD source. 171,784,401 divided by 171,785,445 is 0.99999392265. So I opened the Mic source in Cool Edit Pro and used Effects > Time/Pitch > Stretch, put in 99.999392265 as the "ratio" (which sounds more like a percentage to me, but its default "ratio" is 100 for "no change"). I made sure to check the Time Stretch (Preserve Pitch) mode and left all the other defaults. The result is that the file has GROWN in size by approximately the number of samples that I was trying to shrink it. I think the actual number was in the 1100s, and then when I went back and looked at the settings in the Stretch window it had chopped the "ratio" down to just 99.999 instead of the full 9 decimal places. I'm assuming that's the source of the difference in the magnitude of the stretch, but why did it expand instead of shrink? And is 99.999 good enough? If the end result is that I'm off around 100 samples over an hour is that something to worry about?