There are 3 versions of the HP mount aid in this zip file.
Each version uses a different piece of hardware for the 'accessory attachment' holes,
but all versions are intended to use the same captive studs as usual to mount to your dome.

Brass Insert : this version is intended for using a threaded brass insert
               use McMaster #94510a240 for the M3 insert or #94615a112 for a 4-40 insert
M3 Nut       : this version uses a regular M3 nut
4-40 Nut     : this version uses a regular 4-40 nut