Well, far be it for me to beat a dead horse with a giant zucchini, but since this is the internet, and since sometimes that's its highest and best use - - James, I think we're both right.
I just looked at them for quite a while and I still think that they at least have a rounded shoulder on them. I agree though that they look "flatish" on their very tops.
James, compare these roulettes to all the others of Twigg's in the book. These are definitely different from his other technique. Whatever he did, he only did it on these two rifles for some reason.
Maybe he rolled his cutter as he made his circles on these two rifles. I just wonder how he did it so consistently, almost perfectly, circular. He definitely was going for a different look for some reason, compared to all his other work in the book. It is a stupidly subtle, and probably meaningless detail, but it stands out to my eye as a more interesting look than the standard approach he used on the other guns and pistols.
By the way, I did make a quick hollowed out punch out of an old nail set. It takes just a few taps once a circle is cut to make it into a dome. I'm still just playing with it and have no idea which road I'll take.
Ooops, I've got to go, I think the SPCA is at my door.