Making a rounded corner in leather

A couple times now I've wanted to round the corners on a book cover. When the corners are square, there are plenty of techniques to miter the fold-overs—for example, Eden Workshops goes into this in some depth. For these techniques, however, I struggled to see the geometry working out as nicely on a rounded corner.

A quick investigation on Google produced no help beyond this video tutorial. It seems promising. The basic idea is just to mold the leather over the corner without cutting it. The excess leather is gathered into ridges and pressed down as much as possible, and the pliability of damp leather allows this. However, I must not have the knack of it—there is always too much excess for my taste, creating a really bulky corner which can prevent the book from closing flush.

I wanted two things: a more or less flat profile on the fold-over, and complete coverage with leather in to about 1". To get rid of the bulk, the only solution I could see was to cut darts into the leather. Here's what I ended up doing.

And some actual photos:

I'm not sure if the solution I've come up with is an especially great one; in fact I already know of a couple ways it could be improved. For example, right at the end of the fold there's a small bit of bulging that messes with the roundness of the corner. More than that, there is an obvious fold—two, in fact—on each corner. Ideally, everything would be one smooth continuum. Still, it's a starting point, and I actually find this technique rather pretty and deliberately crafted.

I would however love to work out other ways of dealing with the excess bulk. It does seem possible to create a flat rounded corner without cutting any darts, as seen on the purple Bible here. I suspect some leather has been cut off the corner in that photo, but not very much; the rest of the bulk has been gathered and pushed out to the sides.