Stretching it... warning- wordy!

So you buy a girl a wedding dress- You do not consult her, you just buy it. No trying on.... and then  an adjustment is needed.

Well, to be fair, the wedding dress is rather spectacular, and has quite a good margin for fit with the way it fastens... However, on the back of it is a piece which is a truncated triangle,  which should cover the bare flesh of the back, when the lacing is laced up.
In this case, and she is a very tall lass, the piece does not quite cover.

So, take off that piece, and present it to a friendly soul to make it bigger. We want it 2" wider, and 2" longer.

S-T-R-E-E-E-T-C-H......

I have no similar fabric in my stash- so what to do?

Luckily both sides of the placket are in the same fabric. So, that is useful. It is boned, horizontally across in 4 places.
Measurement?
Starting size is

6" across the top, 16" deep, 4" across the base.

So, I need to end up with

8" across the top, 6" across at the 16" level, and 18" total length.

Unpick everything!

Leaving two pieces, of which I turn one upside down, and stitch back together with the other along a side seam, to give one larger piece of taffeta.

From that I cut a piece 8" by 16" with 6" at the base, Then I take the offcut, and attach that at the bottom, and trim to required size. There is not a lot left over, either.

And then use that as a pattern and cut two pieces of white sheeting to match, and put casings for boning, on that, sew all together, inserting
boning at the appropriate time, to give

I think that should work, yes I added an extra piece of boning, but by the time the dress is laced over the top of this, I do not think a blind man on a galloping horse will know any different!

Another wee job ticked off my expanding list!

And no, I would not buy one of my girls a wedding dress without input- In fact, I would probably make it instead- with input!