I am currently working on a purple Italian style gown. When it came time to bone the back (where the lacing is,) I found that I only had quite wide steel bones (approx. 11mm wide.) I used what I had, but was not very happy with how the lacing looked.
I think the wider bones make the lacing holes look too far apart and too wide.
So I took a chance and ordered thin flat steel and sprung steel bones from an ebay seller. They arrived today, and I am quite delighted!