S,

Regarding the "servo arm straight at full flap". Yes, I know some people favor this setup .. to do it, you arrange the servo arm to be exactly parallel to the pushrod when the flaps are down .. then any force from the blow-back on the flap pushes on the arm in line with the pivot point of the arm and thus provides (theoretically) no torque on the servo. The only drawback to this technique is that small movements in the servo arm position at flap-down provide essentially no motion of the flap (that's the point, right!)

The side effect of this is that you cannot use the radio or a matchbox to trim the flap down position .. you can only use mechanical adjustments. This can make it a pain to trim any slight turning tendency with full flap, or do vary the amount of flap deployed at the full flap position, again since all adjustments have to be done by turning ball links or clevises.

Since we now have servos and arms that can easily handle the forces involved, I typically do not use this setup, but it's a matter of personal preference.

Dave