Richard,
I tried out Epson Exhibition Fibre with K7 inks using the standard IJM curves. The short story is that I get serious mottling from 95%K. Brian then tried it out on his 1900 and gets a similar, but not quite as bad, result. If you have any suggestions, I'd love to hear them.
Here's my summary at the end of the thread:
1. Brian prints on a 1900, I use a 3880
2. Brian uses SE inks. I use Neutral3. Brian lives in a low humidity environment. I live in a high humidity one
4. Brian uses a PC. I use a Mac
5. We both get unacceptable results with this paper.