Just something to keep an eye out for if you're carrying the setup using the strap lugs on the 800PF: after several outings, I've returned home to find a few hundred blank shots thanks to the Z9's vertical grip button been unknowingly switched on. Figured out that it is being caused by the camera strap, which is attached to the 800PF's strap lugs, rubbing against the switch while the camera/lens is hanging at my side, or when I transition it from shooting to hanging.
That vertical grip switch is the worst design feature of an otherwise brilliant camera. I'll either tape the switch, or find another way to carry the rig, probably by mounting the strap to the tripod foot, but I abhor the loss of control as the camera/lens hang+swing upside down from my shoulder as I walk through the woods.
Just watch a Gray's of Westminster video w/ the 600 TC, and they carry the setup with camera strap attached to camera body
While this would solve the issue for me, I don't think that is feasible for a setup of this weight, because the rule of thumb is if lens has place to attach strap, that's how Nikon intends the lens to be carried to avoid undue stress on the mount.