gehajake,

Thanks for the additional info. I don't mind the branches getting beaten up a little in the collar (or even deer browsed). It is the damage to the main leader that hurts, or even kills, a tree.

I think I will split some ruined garden hoses and strap them to the top edge of the collars. That should give a gentler bearing surface for when the wind bends the tree top over onto the top edge of the collar. I may even have some ruined 4" corrugated drain tile. That would be ugly but round!