I live on the OBX so I'm constantly fighting salt corrosion on everything. My thought is to seal the angle to the axle with a flexible adhesive sealant. I want to put a few miles on it first in case there is something that needs to be adjusted or modified. Any other suggestions are welcome. 

It applies to the 3500 lb Lippert "diamond" configuration axle only, and will only address stiffening the axle tube itself, and not any failure that might or might not occur in the spindles, torque arms, or rubber components. 

I had a 77.25 inch long piece of 3x3x3/16 steel angle cut and cambered (crowned) about 3/8 inch in the center. You need to be specific that the crown is made at a 45 degree angle to the angle flanges, pressing on the point or "heel" of the angle.  Be sure to measure your axle tube length and allow at least a 0.125 clearance at each end so the torque arm won't rub on the angle ends. The shop I went to specializes in trailer modifications but any shop with the appropriate size hydraulic angle cutter and press should be able to do it. It's not expensive, the fabbed piece cost me $30.

I ordered four 1/2 inch square U bolts, shackles, washers, and nuts from these very nice folks:

The U bolts need to have a jaw opening of 3.5 inches, I got 6 inch long ones, the shackle, washer and nut stack up is about 1.5 inches but you need some additional length to get things started. There is plenty of clearance under there. The U bolts should go on at 90 degrees to each other, 2 at each end, as close to the ends of the axle as possible while still allowing some clearance to the torque arms. The U bolts and hardware cost around $75. 

Of course, there is no way to ever "prove" that this reinforcement solves the axle bending problem, but if it is caused by the axle to frame attachments being too far inboard on the rPods, it should help significantly.