Ryan, the Norco BAL rep for the frames called me this morning and stood behind the product. They will pay to replace BOTH rear-most spring hangers.
He gave me a full rundown on any issues the welder should be aware of, approved my suggestion for gusseting, said they would pay the welder, and most importantly said he would bring this up with their engineering dept.
So far so good.
Thanks to all for suggestions on gusseting. I'll run these by my welder, and then let him choose an option that makes the most sense.
My inclination is that, since the "saddles" holding the hangers are offset slightly to direct vertical thrust directly up through the frame's vertical "web", I suggested a gusset from about halfway down the "inside" of the spring hanger to the folded corner of the inside of the main frame member. The frame is a kind of Z-folded channel, and this reinforcement is to the "unsupported" side of the channel, but he felt that would add substantial rigidity in both directions.
HE WARNED NOT TO WELD ACROSS THE BOTTOM OF THE ACTUAL MAIN FRAME MEMBER, BECAUSE THAT WELD COULD WEAKEN THE FRAME AT THAT POINT. Good advice. And that explains the "saddles" to mount the hanger bracket.
Fingers crossed that the repair goes as well as the conversation with Ryan.