Hi Jack,

I concur with all suggestions, especially remembering copper and solder mask
clearances thru all layers.  Been burned by this in the past.

I would also recommend you make sure mounting pattern is easy to see or drill
symbol is unigue.  May also want to make note a "flag note" and flag at least
one mtg hole drill symbol.  Will help fab house avoid confusion about which
holes you want countersunk.

May want to check with fab house to make sure your material can be countersunk.
I've only done this myself with FR4 type mat'l in the past and am not sure
if all mat'ls can be countersunk.

Good luck,

Jay (a real "new guy")