A sleeve style prop nut:
http://shop.lindinger.at/product_inf...ducts_id=15942
That makes APC 14x6 to be OK for OS.91.

And you might not needed if use propellers MARO (wood):
http://shop.lindinger.at/advanced_se...sort=5a&page=2

or Graupner-G-Sonic(composite):
http://translate.google.com/translat...006-35,GGLR:en

Well, not every good thing is located outside of Europe.