Update.
His installer came back to listen to them and agreed the StudWoofers sounded terrible. Apparently he was very apologetic. He removed them, patched the drywall and will be back to sand and paint when the seam fill dries. He refunded the list price of the subs. The owner is unsure what he will replace them with as his budget is small but they won't be in-wall.
I suspect he lost a few dollars as I'm sure that in the total package, which wasn't line itemed to begin with, the installer had some markup on the subs. Still, it could have gone a lot worse so he is pretty happy.
