Yeah, thank you!
That's what I have noticed too when I switch a single 572b and a single 811A. I want to make sure.
Also, I have this issue, I have the load all the way down to 0 and anything slightly above that the output drops significantly. I have a 1.1 swr on my vertical antenna. Also, at this low load setting the tubes glow, they glow harder when I set it higher. Do you know how I can get it to where the tubes are not glowing and the power is not lost due to a tuning mismatch? I am operating at 6920 khz and the band setting is set to 40 meters.