I don't think there's an easy answer to the question. Videos show how selective the wood buying process is. Each piece is individually judged on quality, size, usabillity. Esecially older trees, which withstood the test of time, can have some really wild shapes and a lot of branches. The branches area and also parts which were attacked by fungi aren't desired for the production of instruments as far as I could tell. Replanted forrest, under strict human control, seem to produce much more regular shapes (wouldn't you know it), of which an estimation possibly is a bit easier. Still, there are many uncontrolled factors in nature and inspite of our endeavours, the outcome of the tree's quality isn't very predictable. Also not whole trees are bought, only desirable bits and pieces of which the size of the tree also can not be determined, just like the shown example above. The age of the tree is also important for it's size and there may be a correlation between age and flamesize/distance, but this is about all one could determine from the grain on the guitar top. Mind you this is my own assesment, not a scientificly proven one.
Ludwig
