You might want to take a look at the plastic (vinyl?) Duplessis feeders. We've had a couple of them that we use every winter (long, cold, snowy ) for 4-5 rambunctious geldings, and they've survived virtually unscathed.
The first one we got developed a crack during its second winter, and they replaced it immediately.
They're easy to handle and move with a bale spike, and it is possible to shunt them with your shoulder if you must, but I definitely recommend a bale spike.
None of the horses has ever sustained an injury, etc, which is good, and I've noticed that they quite like sticking their heads inside on summmer afternoons when it's buggy out, even if there isn't much hay in there.
If you live near any amish communities, check them out. The fellows we work with for building our sheds also do round bale feeders. They had some nice covered styles that could fit 1 or 2 bales and opened up so you could drive the bale right in with the tractor and bale spike
Irish Draughts and Irish Draught Sport horses
Double use for the money -- we have a field shelter, and a run-in at the back of the barn, both are big enough to tie a round bale up in a back corner. DH screwed rings into the support beams and then he uses hay twine to tie some very sturdy pallets around the front of the bale, which he can tighten up as the horses eat the bale down. Each easily fits 3-4 horses with no fights.
... Reminds me of my safari in Africa. Somebody forgot the corkscrew and for several days we had to live on nothing but food and water. W. C. Fields
Another vote for the Duplessis feeder. I got one last year and the horses love it. I put mine in a fence line so horses from 2 different turnouts can eat out of it. It works well that way for 2 horses per side.