A 3 gallon limit is probably a good trial number. No reason for someone to need more, unless they need the food. Commercial harvesting only generates revenue for the state bureaucracy and limits the availability of huckleberries for the general public. Enforce the 3 gallon limit, and leave it at that. Survey the availability and adjust the limit as needed. If a lobyist indicates the need for commercial access to the berries, tell them to plant them on private land!