I suspect that based on the size of rectangular tubing that you have chosen, you could weld the pieces together in about any configuration and you'd be ok. Just looking at that A-frame, to me, it doesn't look right.

As one other poster said, you should make sure your brackets allow you to move the axle to balance the tongue weight.

And also, I assume you have chosen the axel/springs you plan to use. Make sure your frame rails are spaced properly to accept the axel.

sm