I just finished a Boot Hill 5f1 myself and am very happy with it. I noticed that my initial voltages were very high, I attributed this to the AC output of my home outlet which is 121V. The amp is designed for 110V which is I guess is what was standard in the 50's and doesn't' seem like much of difference but really is. I am running vintage NOS RCA's from 1960 so I really wanted to get the voltage right so as not to prematurely burn out the tubes. My solution was to run a chain of 3 12V 5W Zener Diodes from the PT center tap to ground. Took my B+1 voltage from just over 400V to 343V. The tubes are running much cooler now and have a very nice dim glow. The amp is sounding great too. Pic shows the diode chain on the left on a ground strip bolted to the chassis side wall.