Break Away Cable

Anyone have an opinion as to where to hook the break away wire. The
folks I bought the TT from had it clipped to a link on the safety
chains. I thought it should be attached to the tow vehicle but who
is right. If the TT comes off the head then the chains are the
only thing holding it and that wouldn't last long before they
break or snap off taking the break away wire with it. If it was
hooked to the tow vehicle I would think that the cable would be
pulled and activate the trailer brakes. RV dealers have all different
opinions on this and if questioned treat it like "it don't matter
where you put it". I had the nut on the ball come loose and fall
off, it had a lock washer and I checked often. I got home only
because the shaft was long and jammed into the hitch. You say
how did this happen. Wisconsin interstates especially around Madison
caused the whole rig to "pogo" bounce or porpoise. Others have
experienced this and told me it is because of the expansion joints in their highways.
We don't get this anywhere else in the country.
Now you understand why I'm concerned about the brake away cable.