If the hedge benefits a lot more people than just you and the neighbor, it seems unfair to make the neighbor bear a high percentage of the cost. Maybe it makes more sense to imagine a two-step process: everyone who cares about the hedge puts in some money, then someone is hired to do the work at market rate. If the person hired wants to also donate, that’s up to them.
If the hedge benefits a lot more people than just you and the neighbor, it seems unfair to make the neighbor bear a high percentage of the cost. Maybe it makes more sense to imagine a two-step process: everyone who cares about the hedge puts in some money, then someone is hired to do the work at market rate. If the person hired wants to also donate, that’s up to them.