I have begun some preliminary work on my ACC Sottana, also often called an Italian Petticoat or Kirtle. To do so, I took my chocolate kirtle pattern, and modified it to have a more pointed waist, instead of curved. Since my inspiration portrait is of Eleanora di Toledo, it was a logical decision to make. The Pisa Gown, and Eleanora di Toledo's burial gown (both are extant gowns you can see here), both had a distinctive point in the front, so I used the burial gown pattern in Janet Arnold's Patterns of Fashion for a basis on my lines.
It's hard to tell just by a picture of the pattern piece, but I'm confident that this will not only fit, but will be much more representative of the overall look I'm going for than the curved waistline.
I will not be wearing a separate corset beneath this gown, in the spirit of Eleanora's well known active lifestyle and the belief that she did not wear a stiffened pair of bodies. Anea has an excellent article on this topic on her website. I will, however be stiffening the bodice with boning and cotton canvas in order to maintain the clean lines and bust support my body needs. In period, bodices would have been stiffened with all manner of things, from cardboard to glue-stiffened linen (buckram).