As others have stated, Michael Gurian is still alive and well and involved in the musical instrument industry, though now is making specialized parts for guitar companies rather than the guitars themselves. If you've ever noticed the inlaid wood "Tacoma" logo on the peghead of a Tacoma guitar, that came from Gurian.
As to string gauge, back in the 1970's and 80's I knew a few players who owned and used Gurian guitars. They strung them with either medium or light gauge strings, according to their personal preference and playing style. The guitars themselves are certainly robust enough to handle mediums.
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