The reason that the Trailair Rota-Flex 5th Wheel Pin Box # LC328330 is not compatible with the Curt Q Series 5th wheel hitches is that the head units on those hitches are spherical, which means they don't offer enough stability to be used with the Rota-Flex's cushioning. The same goes for the E-series.
You would need to use the Curt A-series like the Curt A20 5th Wheel Trailer Hitch # C16140 which is compatible with the Trailair Rota-Flex 5th Wheel Pin Box # LC328330. view full answer...