Oh, there IS an image in minmay's post.
Guess I should pay more attention to my own freekin threads.
Yeah, the problem is, as egomassive said, there doesn't seem to be a good way of doing it. For simplicity purposes, I've decided not to go with transparent or antialiasing, and the method I am settling on actually looks a lot like yours, minmay. It seems I have to go with those "parts where the little segment things get longer then shorter then longer" because otherwise the outline is polygonal rather than round. It does look rough, but I can't find a better solution and want this tileset done so I can move on to the other 3 tilesets I've been planning out... wait, I forgot one. 4 tilesets.
As for my snafu on the public use issue... well, I'm not sure yet. I realize I'm being a little possessive, and I'm not sure why. I think for now I'll keep it "ask permission" at least for now. After all, if someone is new to Knytt stories, I'm not sure they should be messing with smooth stone tileset quite yet anyway. I find it takes a bit more planning and rework than the standard tilesets.
Anyhow, thank you all very much for the comments.