I am building my 4th violin. I've made an effort to carve the tops of the first 3 very similarly to each other, from similar wood, for consistancy in tonal result. I followed arching templets matching a Stradavarius style. I am arching my 4th fiddle using templets more matching a Guarnerius style this time, again using similar wood to the first 3. I've heard that some luthiers prefer to do their arching more intuitavely, by eye, not using templets.
I know a good mandolin maker who works by eye, and stresses to me that the thinnest part of the plate must be around the edges so the whole top can move there, like a speaker cone. And there are several other factors like how far in before the arching starts to rise , how steeply, etc. to consider. If you carve your tops by eye did you first practice methodically with different archings before taking off on your own. If so, all things being equal, what are the basic principles to be followed?