I do agree that it is safer to manage before it becomes a problem. The other pony didn't show any of the signs of IR that I saw in the last horses I worked with that had it. The property is by no means 'lush' just lusher than the completely grass-less half acre she is on. It has never been seeded, and to my knowledge is kept mown and is never terribly high.
Thank you for those sites, though. I'm going to keep them on hand for quick reference. I would never have let my pony go out on a pasture like that with no muzzle at all, it was really just the adjustment period I was concerned about. I didn't want to take away her defense, I've seen some pretty nasty fights on first meets and I didnt want her to be left running to a corner.
I am blessed with a mini that isnt a terribly easy keeper, and one who does not like to eat all day long so I'm hoping that between those traits, her muzzle, and the conditioning/training she will be starting when she moves that her weight can be kept down to a reasonable ammount.