Alex i have an idea for the brake mounts. Forget the idea of thin seat stays. Instead produce the stays like a normal frame, but machene the bottom part of the brake mount into the top of the stay. That way when the top part of the mount is bolted in, it will be an integral part of the frame. However to do this you need to have a weighty solid seat stay. Of which ihave no solution anyway, i doubt it would work, just throwing up ideas.