Thanks LegalEagle. I too have replaced the factory brakes about two years back, shackles too, as I see the need. To help secure the underbelly, which was beginning to break loose from it's attachments on the I beams, I have installed tie-down straps, the kind with hooks and can be sufficiently tightened with a ratchet handle. I installed them across strategic points under the underbelly, from I beam to I beam. After 10,000 miles I can say the extra support appears to help. No further sagging.
2015 F250 Lariat 6.7L diesel with Supersprings
2015 339 FLQS Jayco Eagle 5th Wheel
Just Moving Along