There have been countless pages of Zed Threads written about problems fitting newer tubes into classic amps. Some of the problems are solvable (or tamped down to 'workable' situations). I'm pretty sure that someone designing a new RF linear amp around 811's would be accused of 'not dealing with a full deck" for the reasons you are eloquently hashing out here. IMO at least, the 3-500 seems to be about the best 'bang for the buck' if someone wants to use current production valves for amateur use. I went through my whole tube stash and cannot find the 811A's I had to share a picture of the grid wiring. I must have given them away some time ago.