The MCU6500 used on the Lumenier Lux, or the MCU9250 used on the SPRacing F3 Mini, have worse specifications on paper than the MCU6000 and 6050 used on many other boards. But does it matter in flight? Myself and Boris at least seem to have concluded it makes a small difference in the tune, but overall flight characteristics are great. But now at least one person seems to have found a "smoking gun" in the 6500's performance that may mean that, at least for some copters, serious mitigation is required.