I would suggest trying to base the tween frame on a more realistic movement.
You are making a the motion blur. Imagine it as just that a blur of the frames you might see in slow motion.
The arm would face downwards while going into the pocket and swing upwards and bend when removing the item.

I've made a sloppy edit here to try and show my thoughts in motion (it would need a lot of tweaking).
EDIT: I realized your 1st sprite has a bulge. bring it back!
