I've just been thinking about this same issue, and had come to the conclusion that there's nothing for it but to make up a set of differently spined arrows (as suggested above). I also thought it would be a good idea to have a "club set" of these, so that others could use them to test what arrows might suit - at least to get them into the ballpark anyway.
The issue I have is that as I draw 29", the arrows I ought to use will (as I understand it) need to be spined higher than shorter arrows. I guess if we made up a long set, then those needing shorter arrows can adjust the spine needed accordingly once they've got an idea from the long set, as the change in spine with arrow length seems a reasonably fixed rule of thumb. Or is that then getting back to initial guesswork anyway?
