I've jumped from the "favorite seat" to this forum -- because I asked how to find my sit bones. I think I've found them, but I'm not as sure about my measurements. I don't have concrete near my home -- so I tried it on a textured door matt--but the marks are rather obscure--

How exact should it be--and should I err on the side of wider vs. exact when it comes to the seat. I think I"m between 5 and 6 inches, but I'm sure that is not exact enough.

Oh yea, do you measure from the outside to outside of the indents, or middle to middle?