I like the contest the way that it is. One category for "one chunk of wood" bows, and another category for "multiple chunks of wood and other stuff".
It could be disected into 20 different categories; leg sinew backed bows, back sinew bows, recurves, ELB, short bows, longbows, paddle bows, pyramid bows, and so on. If that happened, the BOM contest would be garbage. Just my two cents.