Not sure if this is in the right section, but anyhow...
Found this bit on eBay, and it's almost exactly what i'm looking for except that, I think, the bars are square (from what I can tell from the pic), and I was wondering if this would be uncomfortable in Shea's mouth?
I am going to give you my opinion and move this thread to the "tack" section. You might get more answers there.
Ok- opinion- I think you should skip this bit. A rounded mouthpiece will be less harsh. The square mouth will add more "bite" to the bit. Round will roll ~ Square will not...the horse will get the edge of the bit on it's bars when pressure is applied.
Be strong and courageous, and do the work. Don't be afraid or discouraged by the size of the task, for the Lord God, my God, is with you. He will not fail you or forsake you.