Thanks, Kirk. That solved the problem. The extensions are .on1 and .dop.
So if you had a CR2 file, DSC_1234.CR2, would the names of the sidecars be DSC_1234.on1 and DSC_1234.dop, or would the be DSC_1234.CR2.on1 and DSC_1234.CR2.dop ?
Ideally we would want to have PM consider them as "attached" files such that PM would move/copy/rename them for you when you perform operations on the main image file.
Thanks,
-Kirk