It's my opinion that spending a lot of effort on creating FHM spawning sites is a waste of energy and time in most circumstances... Unless you have an unusual pond stocking scenario, FHM are eradicated in short order after stocking reproducing predators. They did not evolve to live in habitat where predators are found. So they are easy pickings. Spending time on placing spawning structure is mute. FHM are resourceful and will have plenty of places to spawn in a normal pond without any extra effort. Just my 2 cents.
_________________________
Men and fish are alike. They both get into trouble when they open their mouths.