Arnaud,I don't understand about "Does one have to make allowances in the initial blank size before starting, or do you just make "fitzalls?"
A "fitzall" is a universal size, as in one size fits all. I note that many make bracelets for sale at shows and wonder how they choose a universal diameter.
If they are sized, then obviously one would start with a longer or shorter blank depending on the client's wrist size.
Dave