Rick, In my opinion; no, there is no way to rid yourself -reliably- of bow and or twist on an existing PBGA. It would seem to me it is a standard warpage issue that is probably rooted in an unbalanced design, not so much material. A pretty broad statement but I think true. If you are successful in straightening out the curve, I think it will come back to haunt you.... more sooner than later. Coretec Brad