Thanks guys! I'll just use the 1/4" I've got. I assume those are 1/2" holes? And Kraig, you said to make a strap with the slots at the top for using a moldboard plow, correct? That should be fun to do without a milling machine... drill several holes and clean it up with a grinder and file, I guess.
It's not only that I'm too cheap to buy these pre-made, I just like to do it myself sometimes. Stress creator/reliever.