What I did after Orv sent me a template of the Sig handle, I cut the handle out. I then drill the holes for a 4-40 threaded rod to go in the handle as seen in the picture. I then drilled the outer part with a 11/32 drill for Dubro 4-40 threaded inserts. I then put thick CA on the inserts and screwed them into the handle. After than I put some 4-40 ball link ends on 2" 4-40 threaded rods. The rods will go out as much as they will go in, giving a good amount of adjustment. It weighs .7 oz.
I am going to fine sand it and seal it before use, but this is it. What do you think?
I believe you are intending to make one for each plane. For the next ones:
Measure the hole to hole separation on the bellcrank on the plane that handle is for. Mark the center line on the handle and mark the bellcrank hole spacing centered on that line. Drill for your 4-40 threaded rods so that the lines are spaced the same distance as on the bellcrank.
Making the bellcrank and handle spacing the same will give you a 1:1 movement. That is, if you move the handle 20 degrees, the bellcrank will move 20 degrees. With your handle the way it is, if you have a 1.5" bellcrank and a 3" spacing on the handle if you move the handle 20 degrees, you pivot the bellcrank 40 degrees. That is why many of us who started out with 1/2A planes found them hard to control. Of course the same applies to larger planes.
With the handle you have, you might want to make a larger plywood bellcrank to match the spacing.
In any case, good luck with your handles.
George