I was wondering which servo arms I should use on the 2 servos that control the 2 bellcranks,the 24mm 4 arm or the 34mm2 arm one?
I have posted a pic.(Im using H/T 65hb's)
Also I have these 2 little metal balls with set screws in them that I see no reference to either in Bob Whites videos or the instructions,what are they used for?

Those are flybar weights.

I used the 2 arm horns, put the ball links in the second closest hole to the hub. Yup, those are flybar weights, you can put them on right up against the paddles, but that is completely up to you. If you do, the heli will be a little more stable and less responsive.

Use the arm that gets the pushrod as close to 90 degree angles as possible at both ends and that doesn't hit the canopy.

I used the outside hole on the long horns, seemed like a perfect fit to me.