I think the "small" large frame hen size work for them (good example is leghorn hen size).
My girls weigh maybe 3 pounds. Mine seem to "pair off" in small groups so I haven't had too many problems. I have 2 roos to 5 hens.
The boys do squabble a bit but grew up together.
So I'll do the same 10 inch elastic. I need to add lenght, though, because they are loooonger than the chooks. I think the longest one I've made was 9 inches. Is 10 inches too long, do you think. Hum. If I had an extra and thought I could get away with it, I'd have her try one on....