Thanks a lot, Neal! About those hex screws, I measured 4.17mm so about 0.164'' and according to http://www.engineersedge.com/screw_threads_chart.htm it should be #8-32 (and about a half inch long). I tried those screws as a replacement of the phillips screw around the negative stage and it fits well so it's all #8-32 screws for me too. I will probably order them with allen head as it will be easier not to switch back and forth with phillips screwdriver and hex bolt one.