Thanks Tim. I see you actually had this idea long before I did.
The main difference is I didn't use square tubing to get my hitch as low as you put yours. I guess mine may be strong enough then. I trust my welds as well but I will probably add the 1/4" plate re-enforcement just to put my mind at ease. Plus it will allow me to hook my chains some place other than my shackles. (My pintle is broken at the moment).