Hey Ian, thanks for taking the time to leave us a review, even if it's not a great one on our part. We are more than happy to replace the adapter, even if it was broken during the install/drilling process.
At our shop, acrylic is probably the number one material we use from the tweeter adapters to all of our custom a-pillars, we know first hand how brittle it could be, but also having the right setup to drill into acrylic resolves these issues. We use it because of it's strength, but the stronger, the more brittle, just like metal.
You had mentioned the issue was resolved by the shop who installed them, so we did not understand if you wanted to return them for a refund or exactly what was expected. We want you to be happy with your purchase and feedback is always welcomed. Let us know what we can do to make this right. Thanks