Choke + Sag Inducing Resistor Switch

[JD0x0]

Apparently my post got deleted...

but Mercury Magnetics makes a variable choke with multiple taps, you could wire it to a switch and control sag that way

[tubeswell]

Here's how I did it (too), similar to one of the other poster's. When in choke filter mode, the screen resistor takes the screens down about 20V this way, and provides a bit of screen current feedback (which you could remove, if so desired, with a bypass cap on that resistor - however it didn't affect the signal much in this amp, so I left it that way it was)