Originally Posted by corners
I see where you're trying to get to. But your question isn't complete. You need a bit more at the end:
Will stringing a 63 RDC stiffness frame with full poly at 53 pounds allow the frame to play like a 70 RDC frame strung with X at Y pounds?
But even then I don't think there is an answer for you. I'm not even sure whether the frame stiffness or the stringbed stiffness is a bigger factor in the "total" stiffness of the racquet/string system.
But here's a question for you that might lead somewhere: What quality of the 70RDC frame are you trying to reproduce in the 63RDC frame?
Excellent questioning skills there Corners!
OP - There may be other ways, possibly more sensible and viable, to achieve the result you want.