I have a Fender Twin '65 Reissue. I hear of people pulling out two power tubes (the two inner OR the two outer) to reduce power on older Twins. Is it safe to do this on a '65 Reissue circuit board version of the Twin? I don't really want to reduce power. I'm thinking, in a pinch, if I damage a tube (or two) travelling to a gig, I can still play the show. Thoughts?