Put the boom aside as we will now first construct the gamma match. First drill one side then the other side. Mountable on a Camera Tripod.
A Multi-purpose Portable Setup - Working low-earth orbit satellites from any place
This will ensure a centre hole on both sides. More later about the gamma matches and mounting of the elements. I have used this gamma match with several of my homebrew antennas and only had good results. Partly assembled 70cm Elements.