well..
First off, the plans you have are more than likely false. There are no known confirmed Amati Basses period. Several claim to be but none that are agreed upon. So, what ever graduations you have there for Amati is some old bass that is claimed to be and not something that any Amati developed.
On the Panormo, most of his basses I believe are 6mm throughout. No graduations to speak of. Also, the wood is quite hard and dense on the top as compared to softer Pine or Spruce.
That being said, the density of the wood itself will govern how thick or thin it can be. The width, length and arching, mainly the arching will also have an effect on the Top strength or lack of if flatter.
Each bass must be individually evaluated for graduation and not according to some plans of a bass whether the model is true or not.
Another thing to consider is that many of these old basses that have been recently measured or mapped out have either been altered in size or thickness or both. Also, the bass may have lived for a century or two as a 3-string and then converted to 4-string in the last 100 years. That 'life experience' of the bass has something to do with the success or failure of its graduations as well.
Let's put it this way. If graduations were an exact science then all basses made today would sound perfect. The one you have is proof enough that no such science exists. Wood itself is imperfect. Therefor no science in the world can standardize the making of wood products.
Here's a tip for you. If you tweak the thicknesses in the Top, work 'around' that Bassbar and leave a small platform build up of wood around it like a shelf. My Gilkes was made this way and also a full sized bass attr. to Maggini was as well. I was told by one of the former owners of the attr. Maggini that a repair man about 50 years ago or so thought this was wrong and removed the bassbar, re-graduated that platform and re-installed a new bar. The Top sunk in shortly after. Apparently, the old maker was smarter than the repairman but could only roll over in his grave watching his bass get raped centuries later.
Once the wood is removed, it is gone for good. Re-adding breast patches is the closest thing to fixing what was done in error.
Will re-graduating your particular bass get you what you want? Well, maybe what the bass does now is all the wood can do. Then again, maybe not. A thinned top will be more responsive for a time but will be weaker as well in the long run.
I usually tell people that if the Bass doesn't do what they need it to do, get a different bass! In your case, getting it as a gift and the bass being or relative low value in the market, you have little to loose in trying.
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