Think of it this way, all these materials have a certain amount of durability, compression and extention strength. Fiberglass is about the strongest in compression, extention and duribilty from abuse. That way it can be made into more radical forms that retain energy. (Horn being one exception). Bamboo back and osage belly provides an excellent combination of woods and proper orientation to maximized each woods/grass attributes the best. With proper building, a bamboo backed osage bow will shoot wonderful and for years.