Prefitting Simplicity 2621 Elizabethan corset

I mentioned the other day I had cut out the canvas fit muslin for my new Elizabethan corset (called a "pair of bodies" during the Renaissance period).  This morning I decided to unlace my previous Elizabethan and compare the pieces, since I could feel the old one had stretched.  My simplistic 3-layer construction last spring using two layers of home dec plus a layer of cotton muslin in between proved to be useful for actually seeing where the fabric warped from wearing stress:

This is useful ... you can see the channels where the hemp cording is ... those channels were originally straight when I made it last year, and this corset has seen just shy of a year's worth of wearing.  The major stress is definitely at the waist, with secondary stress just below the bust.  The front doesn't lay flat ... the undesirable consequence of using the poly boning so often found in sewing stores ... it has a low enough temp tolerance to mold with just body heat.  My cable ties should fix *that* problem.
Oh, a note about the Simplicity pattern's shoulder straps: according to the pattern they are bias-cut.  Bad idea, Simplicity!!  Darn things stretch.  Now, for my canvas fit muslin, laid over the old finished piece:

I cut the canvas using the same pattern pieces as last year ... in theory they should have matched up.  So my old Elizabethan did the majority of its stretching in the front ... hmmm ... right now I am thinking to extend the center front (which should have been cut on the fold for an only back-lacing bodies) and taking that amount extended out of the side and back, and then "take out" more from CB and CF via seams - 1/4 inch in front and 1/2 inch in back.  I think twill tape at the two stress points will help reduce the warping.  Now, to ponder on the boning versus cording versus combination idea ...