I just finished up a test butterfly straitjacket with a lighter-weight (2-2.5 oz) leather called E-18 from the Hide House. It's a variation on their explore hide (which is 2.5-3 oz). I was curious to see how the jacket would come out with a lighter-weight leather, although I was a bit worried about strength and durability. The cool thing about this particular hide is its almost ironed-smooth finish, tight grain, and silky soft feel...
I figured this would be a good opportunity to show you the steps I take to make the rolled-edge seam along the round breast opening.
The first step is the most daunting: you have to cut round holes in a perfectly good butterfly jacket. Positioning is crucial, and I try to center the nipple in the opening. Another thing to keep in mind: the hole gets larger after you sew the turned edge around it. I cut an 3-inch opening, and after the rolled-edge seam is sewn in place the opening measures a little more than 3.5 inches across.
Once the hole is cut, I sew the 1.75-inch strips around the opening, overlapping slightly at the bottom of the opening. Wherever you begin stitching, that will be where the exposed beginning of the seam will rest. I try to stay a little more than 1/8" from the edge of the opening, and feed the strip while turning the jacket under the needle. I tried using clips to hold the strip in place initially, but find it easier to just feed the strip manually as I go.
Once you complete the circle, you actually want to overlap a little bit to complete the edge.
Next, trim off the excess length.
Apply glue to the outside...
...and inside around the opening.
I kind of skipped ahead here on the pictures, but after the glue sets up, you carefully fold the strip from front to back, cutting relief notches as necessary to make the strip take the shape of the circular opening. When you are happy with the way it looks, topstitch around the opening from the front side to lock the rolled edge in place.