I tested out the motor adapter on a Custom Rockets A.T.W. It is a light rocket which always performed well with 1/2A6-2s. I inserted a 1/4A3-3 into the adapter and then slipped the adapter into the tail of the rocket. It was a bit loose so I applied some tape to improve the friction fit.
The rocket launched, underpowered, arced over and hit the ground. Then ejection occured. Thankfully, there was no damage to the rocket.