To all:
Monoball fix was designed to make use of a series of smaller plates for the smaller cameras which are now available. Yes, when you have a 'Monoball Fix', QR on your head it does not take the older classic plates. However you can order the standard 'Quickset device' on any of the new heads, which can use both the new series and the classic plates as well. So you lose nothing in terms of having to replace plates if you are already invested in a lot of classic plates, and you gain use of the newer series smaller plates for any of your smaller cameras. The Quickset device is now, and has been for several years, available in either knob lock, now also with a smaller knob, or flip-lok clamps. So both styles of clamps are still available.
It is an elegant upgrade for our excellent heads in my opinion without making classic quick set user's plates obsolete.
BTW the new heads such as PO, P1, C1 cube, and Z heads with top pan, actually do not need a leveling base as the pan device being on top will be level after leveling the camera. This is of course true of our new D4 heads as well.