Re: best film for 3800 PT/PD negs
Another transparency material to consider is the one from Inkpress Paper. The K3 inks on the 3800 or 7800 (or newest X880 printers) stick beautifully and smoothly to this material. A nice feature: the Inkpress transparency film is available in just about every sheet size you could hope for. Personally, I don't like the hassle of cutting big rolls of film; it's just one more thing to do, one more stage for dust and scratches, curl issues to deal with, and one more needed clear space for cutting in an already overcrowded studio. ;^)
As a self-serving plug, we now sell the Inkpress transparency film at our store (www.DanBurkholder.com) and we do have the letter size, 11x17, 13x19 and 17x22 (all in inches). The 17x22 sheets are perfect for the Epson 3800. We also have rolls for those interested.
Hope this helps!