Thanks everybody for the advice. I ended up loosening all the spokes , and then used the bench to straighten the wheel as much as possible. I gradually re- tensioned and stress relieved a bunch of times and got the wheel back to 90-95% of what it was in the truing stand. Road test went well maintaining trueness and roundness. A slight tweak to the RD arm put everything else right so all is good in cheap freakville..
