Beyond decoration I discovered there are some simple but powerful concepts one should obey for maximum benefits.

Sound plate: the flater the louder, plate tuning to 3 distinct notes is best.
the density of a sound plate is important (micro holes are better than solidity.) Low density vibrates best when balanced with a pliant varnish.. The back plate is to project sound back and not resonate. Ribs that grow thinner at the bottom of a fiddle or cello will project very well. Bottom + toward tail pin.

High frequency soundposts that go plink are key. As with the density of water sound travels farther. Having a star of david patterm in a higher density inside the sound pate distributes sound in a most efficient way. This can be achieved my leaving as little as2 tenths of a millimeter of material raised above the rest of the 2 plates. The center of the snowflake pattern should be approximately where the sound post will be. The addition of an ultra light low density sound post of a noisy poly foam material will enhance most fiddles when placed to the left of the end of the fingerboard between the top and bottom plates. (upper left quadrant toward the bottom right.(don't know why it works, it just does)

So those are some principles that seemed to work.
Some happened in due course in Cremona when wood was washed of its lichten by being transported downstream leaving empty holes where sap used to be.

In short, think of the instrument as a speaker and thin the contacts at the ribs and see the instrument like a reed that thins at the bottom.

A Strad or a Villiume is subtlety like a reed or a horn with a overall thicker top than the bottom overall. The ever so slight quality of this structure is all that is needed. Overdoing it, is no good.