A friend of mine has a little infatuation with vintage Japanese acoustics, and has a rough time walking away from any that come his way. This 1972 Yamaki 12 string was in really rough shape, with the soundboard sunken like a bowl. He asked if I thought I could fix it ….. who am I to not at least try ….
Tuned it up after the bridge doctor install, and, although the bridge and belly were solid now, with no bulging, the action was still far too high. Back to the drawing board I guess.
With the truss rod now maxed out, the next step was to figure out how to give myself a few more twists on the truss rod nut. I drilled out a couple of washers to create a 1/4” centre hole, slipped them over the end of the truss rod and then reinstalled the nut. It bought me just enough few extra turns of the nut to get the neck into the slightest bit of back bow.
It brought the action down when under tension, but still just not quite enough. With full tension, there was still just so much downward pressure on the sound hole area that the top flexed enough to keep the action up. I figured if I could engineer a support post to help distribute the downward forces over more of the guitar surface, then maybe.
General Guitar Works 
Cool blog post, Grant. I had not heard of a Bridge Doctor before, but I watched the video on StewMac. Nice job!
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Impressive! How did it play and sound after? I loved the “applying upward pressure at the sound hole” photo BTW.
Really like your blog!
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It was quite playable and sounded much better than what I would have thought. My friend has a couple of 12 strings, but he says this is his go to.
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Great work! Loved “gave it a blast of steam while applying upward pressure at the sound hole.” Very creative
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