That planter uses the same plates as the older model 246 which I use. It sounds like you are worrying a little too much about how to select the proper plates. I use a set of medium round corn plates for any corn seed that I have had. My 246 has 3 positions for the drive chain which will drop seeds at 3 different spacings (4", 8", 12" or so). Some sweetcorn varieties (kandy corn for example) have very small seeds, and 2 seeds will drop in each opening of the medium round plate, so I will set the drive chain to the furthest setting. Others, like silver queen, are large flat seeds and will sometimes miss so I will set it to lay down the most seed. Any fieldcorn I have used has worked well with the medium round plates, so I usually set it on the middle setting with that. My recommendation would be to compare your seed to you selection of plates, and choose those that match best, maybe erring a little on the big side. Then place some seed in the hoppers and pull it across the grass, checking out the spacing. Those planters can also be used for beans, peas, and pumpkins. It is a simple task, with a dremel tool and some JB weld, to modify any set of plates to give you any spacing you want. Pumpkins will often be planted with just 1 or 2 seeds per revolution. Those plates are litterally a dime a dozen and many folks have bushels of them laying around their barns. You dont have much to loose by hacking some up with a grinder and/or laying in a little epoxy.
