Design help needed for 4x6v6 amp

[gingertube]

Shared screen resistor is a Mullard idea. The ide is that as one side of the push pull draws more screen current the other side draws less and so with a common screen resistor you get some stabilization of the screen supply.

I have used this in guitar amps but only in those where I don't drive the output really hard or a t higher voltages.

I used in most recently with a cathode bioased 6CA7 running at 380 V for 35 Watts out. I was lovely for that.

Cheers,
Ian