I started reducing the size of my arm drive and also found ways to make it stronger and easier to mount.
How I managed to make the arm turn with the shaft, I used more Vex parts.
They have some little mounts that come with the kit and I cut 1 end off and mount them inside the arm. This gives me something for the shaft to bite into and lift the arm.
As you can see in the pic, I tried not to scratch the arm but I did. This area is hidden by the swing mount and should'nt be a problem.