[Brightcolours]

This is probably a little off the wall, but take a look again at the diagram for the 800mm f/11:  https://cweb.canon.jp/eos/rf/lineup/rf800-f11/image/spec/spec-lens-construction.png

Couldn't Canon take the same exact lens, and extend it less by the difference in the focal flange distance between the EF-s  mount and the RF mount and make the same lens available for the Canon 7D Mk-ii/ 70D/ 80D / 90D?  Hopefully they could use an EF/s mount because the imager circle for the APS-C is a lot smaller than for the FF sensor.  Then use it in live view for shots with and angle of view of 800mm x 1.6 or 1280mm?  Yes, I know it isn't going to happen but imagine all that reach!  If it could AF in live view that would interesting to try.  

Would the 7D Mkii would be able to focus and track?  I don't see why we DSLR guys should miss out on everything!

EF-S has the same mount as EF. Only the glass has a smaller image circle. These RF 600mm and 800mm lenses are for FF, so I do not understand why you would want to see it with "EF-S mount".

In live view you can focus with f11.
But DSLRs can't focus f11 when not using live view, the AF sensor won't see anything at f11 (PD AF sensors do not look through the center).
So it makes no sense to make an f11 lens for DSLRs with auto focus, as it will be a nightmare for support depantments of stores, importers and manufacturers would be flooded with questions about why the lens does not focus on the camera (when using OVF).


It would make sense to make such lenses with EF-M mount.