From the wealth of experience within this forum I am wondering if there are any successful recommended approaches to the early onset of rust heave (no heave evident but some surface rusting) between bus chassis members?
There is a huge difference between chassis heave and chassis rust. Chassis rust you scape and paint it.
Chassis heave is serious and more likely not seen until it has well set in.
The rust is between the rails which forces the rails apart making a gap.
6ml is the maximum gap for cof.