For homebrew, people like to use a very small drill size. This just
    gives them an accurate center for hand drilling and is not related to
    the actual size required.

This assumes that they're using "pads - holes" for their etch resist, so
the "centering holes" get etched away.  IMO, it's not worth changing
libraries or DRC for this - there's a "drill-aid.ulp" or something like
that that supposedly does it for you.

The "olimex problem" is more along the lines of:
1) most libraries have a minimum drill size of (english equiv of) .6mm, and
   olimex has a minimum drill size of .7mm
2) most libraries have english drill sizes, and olimex is metric, so they
   don't QUITE match up.

BillW

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