When I make a full corset I use an 11 inch busk. Won’t a ten inch busk be too long in the waist cincher?
If you are comfortable with an 11 inch busk you will probably be comfortable with a 10 or 9 inch busk in the waist cinchers. If you are concerned cut the front of the corset in scrap fabric. Mark the waist. Hold it up to your body in front and see where the top hits. About 90% of women are comfortable with a 12 inch busk in the full length corsets in pattern #100.