Shout Out to the Experts: Fixing Puckering Silk Princess Seams

Egad, I'm back in the sewing saddle (sort of), making a second Pendrell Blouse using that cerise silk I've been to scared to use till now.

All was going very well (figured out how to do the inside binding technique that Tasia instructs in the pattern, which I glossed right over, by accident, the last time). The fabric, while it does water stain (tested on a scrap), did not shrink when steamed. It doesn't fray much. And I've figured out there's likely a very small amount of lycra in it. It has notably more cross grain stretch than any other of my other silk charmeuse. Since it's a fancy fabric, purchased from a designer who bought it from a mill, I imagine this was designed with RTW in mind.

And this, I sense, is the reason why my princess seams (and none of the others) are puckering.

Note:

• I'm using a 60 sharp (recommended needle for this kind of fabric).
• I've tested every tension on my machine (apparently lower tension is better for silk but it produced more puckering for me than higher tension - though the stitches are tight in that fabric...)
  
• I am using poly thread (which may be encouraging the problem, I realize, as the poly stretches in the stitching and then bounces back when sewn, but I haven't had this issue with other silk I've sewn.)
• Note: It's the slight stretch in the fabric itself which I suggest is causing the tension tug back after the sewing. And maybe the poly thread isn't helping. But I don't have ready access to cerise coloured silk thread.
• I have pulled on the seams to lengthen them. Hasn't done much good, but hasn't done any harm.
  
• I haven't yet pressed the crap out of seams from the wrong side - my next plan of attack, after rest- hanging the shell overnight on my dress form. I realize, short of ripping out the seams - a very risky venture with silk charmeuse - this is my best remedy attempt, unless someone has another suggestion.
  

It's very frustrating to do everything by the book - and to produce increasingly thoughtful, sound workmanship - only to encounter the ever-looming "sewing challenge" 3/4 of the way through construction. Really, sewing is so much more stressful - so much harder (IMO) - than knitting. I mean, it's harder to find the perfect material to work with, then physically harder to cut it out and mark it up (just that takes hours). Then you've got to sew it up and hope for perfection though something is bound to go out of whack at any moment. Then you've got to figure out the solution to the problem. Then put it into action it, all the while, hoping that said solution will a) work and b) not cause another challenge. Natch, knitting has its hard moments and some of these same challenges but they seem to happen, relatively speaking, at the pace of a snail - and sitting in the garden. And you're never totally fucked with knitting; you can always rip out the stitches and remake that fabric. It's the process of addition, not subtraction, that creates the knitted garment.

Ah, I'd forgotten that lovely sewing anxiety buzz, coupled with a headache from scrunching for 8 hours. It's not ameliorated by my inability to dull it with a nice glass of wine (see here).

So experts, what say you? Please tell me the pressing's gonna work. Or suggest another solution that doesn't require ripping out the stitches or finding silk thread.

Thank you.