Errrr, 572B tubes are far from Fragile. Voltage doubler conversion would over volt the 572B rated at 2700 volts for NOS and 2500 volts for Chinese plus the smaller Ameritron transformer would not like the extra load. Next, you would have to install more capacitors to meet the higher voltage. I owned an ALS-600. Trips out with SWR at 1.5 to 1 without an antenna tuner. A tube amp will tune out SWR at 2 to 1 to flat SWR. So, just as many knows to turn.