In vid1900 guide https://pinside.com/pinball/forum/topic/vids-guide-re-populating-playfields#post-4526507 . He states a hole about 2mm deep even though the section is about reinstalling wire guides, he references for post holes also. I think there is also some play field install information on Ron Kruzmans thread. I see vid1900 guide he shows metric drill bits, I wonder if there are smaller increments in those that might be closer to the smaller holes needed like 1/16 to 3/16 for screws and posts.