vote sticky as well!
Also there is also the 5 watt screen grid resistor mod.
I had that done on mine after a blown tube took one of mine out. I'm not sure if that value is the same on simul models or just 60 watters. It helps power handling for high powered tubes.
edit: nevermind, just read the (2x) 2700ohm 2 watt screen grid resistor mod. I suppose the value is different.