I use a cinch chix net on my roundbales and have a couple 1inch mini nets from them that I will fill up in the summer and throw out for them to eat on if they choose. There is no way they can get stuck in there, and having a big round small hole net filled with hay is entertainment for them if nothing else. I also use the nets from chicks saddlery, but I hang those up on the barn on tying rings. I fill 3 up for my 2 horses, around 10lbs a piece, and they'll last all night and still usually have some left over in the morning.
I did learn the hard way to use a ring feeder in addition to the big bale net on a round. Once the bale collapses it starts to go flat and the horses are able to step on the hay and soil it. I also now put the round on a pallet to allow some airflow, otherwise the bottom gets wet and moldy and is just a big pain in the butt to get out of the net. Other than that, I LOVE LOVE LOVE my cinch chix nets, my air fern is at a healthy weight, even though he has hay in front of him at all times, and my filly is also at a healthy weight. Both are eating more naturally and my gelding isn't showing feed time anxiety anymore. You know, "FOOOOOOOOODDDD I WANT MY FOOOD NOW!" Type behavior. They are both calm and happy.
As far as nets injuring teeth, I feel the benefits of feeding this way FAR outweigh the risks of NOT feeding with a slow feeder, net or otherwise. Lower incidence of colic from gorging on hay (hoover) or sand colic from feeding on the ground, less chance of founder/laminitis because of being overweight, is absolutely critical for an ulcer prone horse who needs hay in front of them at all times and to be eating at natural rate, constant small quantities. It also helps with boredom and other destructive and/or dangerous behaviors that are almost eliminated when using a slow feeding system such as feed aggression and possessiveness, because they eat all their hay and have to wait hours and hours for their next meal. Horses are accident prone creatures and will find ways to injure themselves doing almost anything.