My rationale was as follows: the risk of too thin is structural integrity and harsh, too bright sound. Too bright fiddles work well as octaves because more resonance is a good thing to bring responsiveness to bass notes. And structural integrity didn't concern me because it is just a prototype, not something I am selling with my name on it to someone to last for 100 years. However, I took it too thin in one spot during tap-tuning it and it may very well pop like a grape when I string it up, so this was probably a mistake.
http://www.maestronet.com/forum/uploads/monthly_12_2014/post-77209-0-55870100-1417934982.jpg
Before carving, I marked the plates with this Strad style punch marker, detailed in the last post:
I used the Strad punch from the earlier post and graduated aggressively, leaving a thick spot in the soundpost area. I held it to the light to eliminate thick spots.
Then I attempted to tap-tune it, simply, just Mode 2 and 5 to start out with. I used mostly platetuning.org info and the free program Audacity. I did this on a laptop using just the built-in mic. When thinning according to his diagram of where to thin wasn't working well, I clicked through to his original sources on where to thin to affect which modes, and used those sources instead:
http://www.platetuning.org/html/modes_-_tuning_plates.html
That's when I almost scraped a hole straight through the belly. It is bad, but in my ignorance I am not sure how bad. It is about 1.9 mm. Maybe a little less. If you pinch the thin spot you can feel your other finger through it.
Even so, I was unable to bring it exactly to the appropriate frequencies.
I began with:
Belly M2 206 Hz
Belly M5 354 Hz
Back M2 182 Hz
Back M5 408 Hz
I settled for:
Belly M2 196 Hz (should be 177 Hz)
Belly M5 354 Hz
Back M2 176 Hz
Back M5 366 Hz
Next time, I will be much more conservative and tap tune much earlier in the graduation process.
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