When installed is this addition visible JaPes? If not and your buddy joins you you could do a blind study. He walks away. You either install or not. Hand him the weapon for evaluation. He takes notes. You each repeat this process a few times. That way there is no perception involved KNOWING its installed. It's only a feeling the gun gives when fired. If you limited shots to 10 per round the entire study could be done with 80 rounds...40 per shooter. 20 with and 20 without - without knowing the order.
The only problem I see with this is the probably lack of the standard buffer *twang*