Please tell me, if Micheal did not modify or block/remove the original vents in the F20 connector in any way, how would he be at an increased risk of CO2 rebreathing? If any, I reckon he has increased the venting instead, cos now there are two vents, one on the F20 connector, and one on the N20 con...

There is a very good, clinical reason why the HumidX system is only approved to be used with the nasal and nasal pillows masks, and not the full face mask. The full face mask + HumidX can lead to CO2 rebreathing that is outside of acceptable standards. Your logic (F20 works with AirMini, HumidX work...