Yer right, we did void the guarantee. (I doubt Joe had one on his old Silvertone back then.) But my Martin had no problem taking the extra 3 treble strings. (Some would say it was more "treble" than it was worth. But it had a fine sound.)
I tuned down an entire note & kept a capo at the 1st or 2nd fret. No altering was done to the bridge; I just put the 2 first strings into one hole and the 2 second strings into the second hole. One bridge-pin in each hole still--of course. And it did help me get more sound with less work--which was what I needed at that time.
It was worth all of it just to see Mike Longworth's reaction every time he'd stand there and gaze at it in Winfield! It really was.