ARINC 408 (a) 5 ATI size
HI, I was doing some web searching and ran across this post. I think I can answer all of your questions. The 5 ATI cutout is 5.010 X 5.010 and 6.395 across the corners. The location of the screws are 4.810 on both the x and y axises, centered on the cutout. Arinc 408 (a) does call out bezel sizes for the standard ARINC bezels also. If you need more info let me know. I am considered one of the ARINC 408 experts in the field of Avionics Mounting.
Regards,
Dean Johnson
Avionics Mounts Inc.