Thanks for posting this Rich.  I always enjoy seeing what you are up to in the cold North.  I think that I agree with you for the most part, and I think I have identified one factor that makes these bows so prevalent.  I cut all my own bow wood and use a lot of white woods and a lot of osage orange, and regardless of species, it is much easier to find a stave 5' long or a shorter, that is close to perfect (no knots, cracks, imperfections of any kind) than a six foot piece without some type of imperfection to deal with.  I have no doubt that the Native Americans found out, as I have, that a perfect stave,  52" long makes a helluva bow - likely much better than a longer stave which has areas that are not so perfect.  I am just saying that long perfect staves are much harder to come by in nature than a shorter one.  I like my longer bows too, but if you dumped me out in the woods with a hatchet and a knife to root hog or die, I would be looking for a shorter bendy handle bow.  Merry Christmas!