Ryan how about just using cold roll and then covering inside and out with POR15? Galvy is expensive as you know and if the tongue is well coated with a paint like POR15 and able to drain it will last most likely longer then you will keep it.If you bolt it together then you can dump the paint in the tube, roll it around and end over end to ensure complete coverage and not have to worry about burning the paint off putting it together.. My Yacht Club trailer has a 3x5 tongue that is through bolted in 2 places with 5/8" bolts.. No welds.
Would recommend double-checking the tongue jack mounting position. It needs to be able to swing freely, also consider sharp turns without encroching on the ball/coupler. The one on the 22-2 barely fits in the up position... wish had a little more space....