Now that I'm back in front my production machine I can confirm what I said before. Ilford Smooth curves are perfect for Platine. For CRP I used the HPR curve. As shipped it was fairly close, just a little dark across the range, but something you could live with. Fairly easy to relinearise either directly in the qidf/txt file or via the QTR-Linearize-Quad droplet. HPR is a pretty good starting point for most matte papers.
Let us know if you need any more info, John. I'd be interested to hear how well the 3880 curves migrate to the 7890.
Are you still printing on CRP? Wasn't it you who was having batch problems in it under the new ownership of Canson?