I've made a couple of these, and in my experience, you really don't need to make any of the pieces smaller or anything like that, you can stack same sized pieces of denim fine. I'd recommend using about 4 pieces of denim, though. I used Liquid stitch (a cloth adhesive you can get at walmart) and it gave a pretty stiff strop, and it stopped the edges from fraying. I don't know how it would compare to rubber cement.

I also stitched one and the stitches really didn't seem to be a problem. I mainly used the liquid stitch because it was easier then stitching, at least for me. I'm not a 18th century sailor or a seamstress.