Hi there Meliodas!
I don’t think steel cord is a technical term… I’ve seen it mostly as a descriptor for guys who have trouble stretching or growing beyond a certain BPFSL despite significant attempts at doing so.
Back in my day (I’ve been absent for almost 4 years) Ultrasound wasn’t really a thing, but I know that people have continued to make gains using any number of methods (hanging, extending, cyclic pumping etc.) to push past their plateaus. Just try a few things. If they don’t work, try other things! Always monitor EQ.
February '16: 173 mm BPEL (6.81") 132 mm MEG (5.20")
November '18: 190 mm BPEL (7.48") 137 mm MEG (5.39")
Goal: A sustained 7.7" by 5.8" during intercourse