I don't see a need for more bracing, unless you do it for looks, you said that the wheels are centered front to back. If the tongue bends it's going to bend between the hitch and the front brace, not between the the front brace and the axle (I can't see how it's put together behind the clip though), longer the tongue, the weaker. If it bends easily, then you need a stronger tongue (not always a bigger od), not more bracing.
Your not hauling a motor or tranny in it (Which I think you could if needed to), just coolers, clothes, lawn chairs, food, beer, etc, and a heavy glass front clip, with rotating/high weight
I like the tank on the front idea.

My .02 worth!

Pat