Yes, Jonathan, I'd usually agree with your logic.

However, this is how I understand it so far, the tubes have a recommended trigger and running voltage. The power is controlled by PWM, so the voltage doesn't change for a tube and PSU pair. But higher and lower power tubes require a matched PSU. The tube lengths are specific to each power level. The 40w and 50w seem to be very close, so I am assuming it will be ok. (you know what ASSUME means ! ).

I wondered if a lower trigger and working voltage in the 40w PSU would be enough to run the 50w tube ... think, putting a small engine in a big car ! ... if it does manage to fire the laser .. might it shorten the life of the PSU ?

Just picking brains, before I try it anyway ! lol

unless , of course, anyone has a valid reason why I shouldn't :)