Hey Miguel,

Yes we do use a 1 inch arm for torque measuring when testing servos.

the difference between teh two is that the 8611A will fry its amp if you stall it. The 8711 will drain the battery quickly if you stall it, the amp will not die. Just for reference, I am installing 8711's on my elevators and rudder of my BVM twin Rafale, and 8611A's on the ailerons, and canards.

Hope this helps.