Do you know how long it takes to stitch a strip of wool fabric onto the edge of a semicircle of fabric that has an (approximately) 48 inch (120 cm) radius when you're doing 5-6 stitches per centimeter?
Far, far too long. I'd do the math to compute the exact distance around the entire mantion, but knowing the exact figure would depress me too much.
At this point, I have sewn the strip of sky blue wool that I'm using for trim along about 36 inches (90 cm) of the distance around the edge. My attempts to come up with a ballpark figure without computing the figure suggest that that's only about one-fifth of the total length.
And that's only on the front side of the edge. I decided to sew the trim to the front and the back side of the mantion separately, assuming that the stitching would go faster because I wasn't trying to catch the edges of the strip from the front and the back together with each stitch. But that means that I'll have to sew around the entire edge of the mantion twice--once on the front, once on the reverse. (On the other hand, once I've done that, all I'll need to do is sew two loops onto the chest area edges for the brooch pin to pass through, and I'll be done.)
But it's still going to be a long slog. I think I'll start work on my fitted wrap-around apron dress in the meantime.