Heavy lift coaxial engine mounting
Fit the engine to the alloy engine mount disk - noting the "chamfer" for the
countersunk machine screws on the back of the part - fit all 4 screws.

Fit the boom bracket part with the inner machined locating dimple.

Fit the second boom bracket part (the one wothout the inner locating dimple)

Fit the sceond engine and alloy mount and install the two nyloc nuts, just
start the nuts on the thread.
Slide the assembly over the boom and locate the dimple into the
hole in the top side of the boom...and then tighten moderately.
Add the heatshrink to ends of the wires near the engine to aviod abrasion
and feed the wires through the booms.