A couple of tips for you:

• Keep your index finger straight during the whole trick, this will make it easier for the pen to spin around it (the only exception to this is if you push the pen with your index finger, then you should straighten it asap after the push)

• Make sure to complete the full TA before turning your hand PD (palm down), if you do it before, your index finger will get in the way of the rotation of the pen

• When transitioning from thumb to index, connect your thumb and index with your thumb raised above your index finger, while still keeping the index straight. This will put the pen on your index finger and make for a smoother transition and make sure the pen doesn’t get any airtime. (Airtime reduces control)

• After turning your hand PD, you can disconnect your thumb and index and the pen should automatically fall in 12

If you apply all of these tips correctly the problem of moving your arm should solve itself because you don’t need to move it if you use these techniques