Anyone have basic plans for a keyhole feeder?

[LFRJ]

I had a magazine article, but the durn thing is awol. I have read the pros and cons about them, but we need something with a bottom to prevent waste. The alfalfa we're getting is practically powder - hay racks and cattle panel feeders would be useless. I can figure it out for the most part, but need a few angle and measurements for the key hole openings. I think its 4 inches or so.

I've searched the net, but can't find anything. If someone has a link they could share, I'd appreciate.

Thanks in advance.

LF

[Alice In TX/MO]

Scroll down (way down) for a pic of a variation that I like. Less likely to trap heads.
http://www.goatwisdom.com/ch9husbandry/shelter.html

It's on about page four, I think, includes measurements:
http://www.abe.psu.edu/extension/ip/IP728-26.pdf