I'm not familiar with that plugin. However, the 'disable state' option in my plugin 's parameters can be used for exactly the scenario you describe. Try putting it as a passive on the arrow weapons and see how it works out.
I'm honestly not sure how it will work out with the arrows being weapons, though, so you might need a more creative workaround. Technically, you could make them shields and they'd still fit in the offhand, and their base parameters would be added to the single attack of the main hand weapon in that case. They'd need to be etypeId 2 specifically for that to work without modifying my plugin, though. You'd probably need some special equipment requirements to prevent a player from equipping arrows as a shield without a bow, or something as well.