I'm looking for 2 papers. One is less difficult to find, but I'll take any other suggestions. The first is a 2 sided paper for using in handmade books--my own. At present I've used the Epson duo sided matte, have ordered the IJA Duobrite longgrain matte and have tried the heavier weight (just for sampling of image quality) of the Red River Premium Matte (which I used at one time with the 1280). They have a 5 mil. duo sided Premium matte that may work.
The other paper is a pigment ink printable vellum--the thinner, the better. I've tried some vellums that have been around for awhile--some Proart vellum--16 lb.. I'm printing with a 3800 so added some drying time, set the platen gap to narrow, and decreased the ink density. I knew the inks wouldn't dry easily--but they did with a bit of time. This vellum is not bad--but have no idea where to buy more---its been around for years I think LOL and I'd really like an even thinner vellum. The Red River vellum is not recommended for pigment ink--so it may have the same issues, but this did dry. I will use primarily between heavier papers--and with primarily text, probably not photos--altho' possible graphics (I did text in several fonts, handwritten with Wacom pen, and some graphics 'sort of' with various brushes. They all did pretty well in black).