I think that 20mils hole was used to serve as drill guide for manual drilling.
crosses at hole centers.
Ability to reduce holes would be usefull also for those who have to use postscript to cerate masks.
None of these ideas is right. The drill sizes should be the final hole sizes, and if you want a small dimple to help you get the hole centered, choose the "drill helper" option when you print your postscript files. That puts an EXTRA circle in the middle of the hole just for this purpose.
OK. I forgot that when I talked about crosses. Sorry for the added noise.
-- [ ]'s Walter Fetter Lages <mailto:w.fetter@xxxxxxxx> <http://www.eletro.ufrgs.br/~fetter>