Let me share briefly some of my findings for Cremonese cross arches. Most back plate cross arches can be fitted to a CC which is a tangential cosine and sine function. However, fewer top plate cross arches are true CC’s. They are often cosine and sine functions tangential to a connecting straight line of varying length. These can be found on some back plates too. On some Strad’s I found a compound sine (two sines) connecting tangentially to a straight line that runs to the cosine trough which are 4 functions. My take away is that it is a complicated story. Calling these curves CC’s is not an accurate picture.
Pardon me if I drop off this thread. I have bigger fish to fry.