When I feed hay, which is not very often, I free feed, irrespective of how much they eat.
I have had horses that I thought would pig out on the feed, but found when I removed the competitiveness form the situation, that they settled down and ate properly.
I use square bales, not round, just ordinary small bales, and my nets take half a bale, so the stallions get two of those between four of them and they just pick at it throughout the day and night.
When they are grazing, after all, I do not limit the amount of grass they eat, so why limit the hay?
Unless there is a medical reason why this method should not be used it is the most sensible, I am afraid I have neither the time nor the desire to go out every ten minutes to give them another handful, it is less labour intensive to feed them a bale and change one haynet every day.
(I used to use racks but they disintegrated eventually and I have never got around to having them mended, they are the best way to go as they hold two bales each, but the small holed nets, correctly tied on the fence, are perfectly safe.)