Thanks Rob, I appreciate it.
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Very much did not care for the smallish pivot point provided by the Italeri design of the crane base as it allowed the crane to wobble a lot. Thought a somewhat larger shaft diameter and more solid attachment to the gear ring might make for a more steady connection.

As Doc Brown would say; "I apologize for the crude quality of this drawing and the fact that it is not to scale."
(Back to the Future; Parts I, & III). . . . . . . . . . .

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The blue coloring represents glue. I did not make any attempt to build any sort of physical locking retainer for the crane turntable assembly. As of now it just fits very snugly into the base as built on the vehicle and can be lifted out when maintenance is required.
This time I used Plastruct tubing
#90604 1/8" and
#90605 3/16". These two sizes telescope rather tightly into each other and therefore provide a snug "push to fit" bearing connection for the crane base.