After hours and hours of desperate searching and speculation I have finally made the decision. I abandoned the idea of a doublet, since I really couldn’t find any reference that would match the description. Instead I found a portrait with a square-necked kirtle that matches nearly perfectly; the only thing that’s different is the same color and fabric for the whole kirtle, while the material of the bodice in the kirtle that’s going to be recreated is different from the skirt and sleeves.
The whole thing is typically Florentine and has all the elements and accessories that can be found also in the catalogs. In addition to that, given Catherine’s connections to Northern Italy I think a Florentine dress can well be used as an example.
I’m going to use Eleanor de Toledo’s burial dress as a guide to help me especially with the details like pleating the skirt. Otherwise I’ll draft (have someone draft, that is) the bodice following the lines of the petticoat bodice.
The down side to all this is that I’ll have to return to the embroidery and construction of the shirt -I was thinking that with the high-necked doublet I wouldn’t need to finish it just yet. I will also need a partlet. And a veil. And a necklace. And a girdle. And the gold coif. And I got four weeks. Think I’m going to make it?