The pattern was based on Waugh's 1880s in Corsets and Crinolines. Of course I had to change it a bit to fit me. I resized the pattern to original size, measured the circumference at hip, waist and breast level, and compared them to my own circumference minus a bit to allow for lacing. I divided the difference by the number of pattern pieces, so that I knew how much I had to add to/subtract from each pattern piece. I also looked at the front-back ratio: Some people have the same back width as the person the corset was made for, but a lot more breast width. So apparently all the additional width is generated in front and should be added to the front parts, not the back parts. Likewise, a person with a hollow back would need some width taken off the back parts around waist level, but if their circumference was the same as in the pattern, that subtracted width would have to be added in front.
I changed the pattern according to above guidelines, made a mock-up of very firm fabric, already with some boning in, and tried it on. It was too wide and far, far too long although I hadn't changed the length and am not all that short of rump. I marked all the places where it was too wide, took apart the mock-up and generated a new (shorter) pattern out of the changed parts. I made another mock-up from that changed pattern, tried it on, and found that it was almost right but for some little changes. I adjusted the pattern again.
Then I thought it was time to seriously make the corset from pattern pieces that, after two tries, should have fit. It did fit, at first. More of that later. I made the foundation of two layers of jean fabric, with steel boning sandwitched in between according to the original pattern, i.e. one along the seam and one down the middle of each piece. The tunnels that kept the boning in place were done by machine.
I sewed all pattern parts together, made a lining (cream cotton) and cover (black silk satin) off the same pattern, placed them all onto each other, basted the edges together and neatened the edges with bias tape. And hammered the grommets in.
All was well until I tried lacing quite tightly. The waist gave quite readily, but around the hip, there was too much boning in the way. Apparently the waist-to-hip ratio was not what I'd anticipated. After little while, it became quite uncomfortable around the hips, being too narrow. I ended up taking the bias tape off the bottom, cutting open two seams from bottom to waist level, and inserting triangles into the gaps in the base layer, lining and top fabric.
After that last change, it's a teeny bit wide around the hips, but since wide hips were fashionable then, that's not a problem. What's way more important is that it fits without being uncomfortable, even if I pull real hard on the laces. I've learned that Victorian corsets have to fit snugly and leave much less leeway than 18th century ones, so if you want to avoid the fitting oddyssey I've had, try a commercial pattern.