Some time ago family of boom block for multicopters has grown. Just draw and cut few next members of motor mount family compatible with boom block for 25, 28 and 30mm diameter of arm. Below is family photo:
New motor mounts are optimized for holding motors with large diameter. Biggest rotor fitting in the contour of the screws can have 69mm diameter. Biggest known motor with 87mm rotor like T-Motor has slight lift of the bottom part, so also should be used here.
Holes for screws are the same in all 3 mounts. It differ only with boom block mounting holes.