If you are making your own feeder putting a waste tray on sounds like a really good idea. I had so much hay waste from my three Ryelands last year, feeding from the ground, that I spent ages trying to work out why this was happening and how I could reduce the waste but not cost me a fortune. When I put hay on the ground they were so busy pushing each other out of the way and walking all over the hay as they did so, that very soon they had spoilt the hay and wouldn't eat it. This year I have bought a four feet long, hook onto a hurdle, hay feeder from our local Wynnstay store. I keep a six by six (with one side normally open) hurdle pen in their field, for any inspections/ treatments, and have hung the feeder on the outside of one of the sides. The four sheep choose which side to feed from (I now have a very cheeky, castrated, welsh mountain ram lamb in with my ewes). As Sally recommends, they have plenty of space per mouth. My Ryeland heads are too big to go through the bars of the hurdle from the inside but the welsh does poke his head through sometimes if he goes to that side. I worried about it at first, but he doesn't have horns to get stuck and seems to go in and out easily. Only a small amount of hay ends up on the floor and that gets hoovered up quickly, after the hay in the rack has gone because, I assume, no dirty feet have been trampling it. It is working well for me, at a fraction of the cost of any free standing feeder, with or without waste tray, that I could find.