I decided to handle re-knitting the Manon in a somewhat systematic way. First, there was no way I could just rip it all out, even though I was pretty sure I was going to re-knit the whole thing.
Instead, I started by ripping out the top back and front stockinette sections and then knitting the center back triangle with that yarn to see what sort of difference that would make in the size and drape of just that piece. Turned out I liked it quite a bit more, so I cast on for the right triplet and picked up stitches along the right side of the center triangle. I finished the right triplet before I ran out of yarn.
Here's how the original, too-drapey, wrong gauge peplum looks next to the new, improved, just-right drape, correct gauge peplum. Or rather, how the new peplum looks on top of the old one.
Here's an up-close look at the original center triangle
And here's a look at the new center triangle
It's really hard to see a difference unless you hold it in your hand. With the original one, it felt like it would end up stretching out over time. The new one feels like it will hold its shape.
I made one change to the pattern based on two things: the way the picked up stitches for the stockinette looked in the original knit job, and another knitter's modification that made that transition point look better.
After you work the back triangle, you're supposed to cast on a mess of stitches, which will be the base for the horizontal ribbing for the right front as well as the two triangles that are not attached to the center triangle. Then you pick up stitches along the right side of the center triangle, which will become the base for the third triangle of the right triplet, and then you cast on 18 more stitches, which will be for the ribbing across the right side of the back of the sweater. The pick up row is a RS row. On the following row, the pattern says to establish the 18-stitch ribbing by working (p1, k1) 9 times. That would give you a knit column for the selvedge on the RS, and would give you a purl column next to the edge of the adjacent triangle. When you then go to pick up stitches across the ribbing selvedge, that knit column ends up on the inside of the sweater, and the stockinette transitions from the purl column. Here's a really crappy picture of how that looks:
That purl column ends up looking like a sloppy pick up. The notes I read from another knitter showed that she changed the ribbing so that it was established on the WS as (k1, p1), which meant the selvedge column on the RS was a purl column. This puts the stockinette at right angles to a knit column, giving a much neater appearance. It also puts a knit column adjacent to the edge of the triangle.
There was one other thing that had bugged me the first time I knit it, and which sent me back again and again to check the instructions the second time to confirm I wasn't missing something. The center back triangle has 3 garter ridges at the base (6 rows), but the triplets have a base of only 2 garter ridges. I went ahead and knit it this way, even though it bugged me and it wasn't until I was well into the second triplet that I looked closely at the photographs illustrating the pattern. The photograph clearly shows 3 garter ridges on the triplet. The inset photo showing the back detail also shows that the ribbing was worked as (k1, p1), not as the specified (p1, k1). The errata for the pattern only corrects stitch counts for the right triplet, and not these two other errors, neither of which affects the shaping of the garment, but only some fairly minor aesthetic details.
Onward and upward. I'm well into the left triplet now. I had to rip out the original peplum in order to recover the yarn to do it, so all that is left of my original knitting are photos. I expect to finish the left triplet some time tonight, and then it's on to the stockinette back...