Overweight Drafts

I'm wondering if this would work. I have seen them in person, and they claim that they are heavy duty and the horse CAN sling them around no problem. You can see it in the video.....
Porta-Grazer

This one is cool, but there is no way it would work for my horse....
Slow Feeder Saver Hay feeder

My mare has a VERY heavy duty shipping crate....looks similar to the fruit bins the farmers use, but is much more heavy duty. It weighs at least 100lbs itself. She will take her hoof and make it look like Stonehenge like it is nothing. I now have it tied to a fence post which is a railroad tie cemented in the ground five feet with heavy duty strapping.

I just use hay nets for my blubberous drafty :P I've went from using about a bale and a half to just about 2/3 a bale per day. I started with nets with really big holes, just so she could get used to pulling the hay out, then gradually got smaller holes. Now she has hay in front of her all the time, even if she can only eat a bite at a time. Hay nets are way cheaper than those box, but probably a bit less effective :P
A lot of people also realllly like that those boxes allow the horse to eat with their head down.

I saw someone make a really nice slow feeder. They put the hay in a hay net, then put the net in a muck bucket (the rubbery kind that are flexible) with a whole cut in the bottom middle of it. They put the hay net's tie through the hole in the bottom and tie a big knot so they can't pull the net out. This way they can kick it all around and step on it, but not shake out much hay, and the net slows their eating. My only thought about this method is you've GOT to be sure the net and the bucket have no loops of a size that the horse can get a hoof caught! Make sure the net's got tiny holes and the horses' haven't ripped any larger holes in it.
I've been using my hay net for 3 months now and she hasn't damaged it at all.

We use a slow feed hay net, it works well and has held up well for us.