Thanks, Wayne. Ilford's profile for the Galerie Smooth Pearl using the Epson Semi Gloss as the base paper worked just fine. Incidentally, the GSP's texture is not as deep as the Epson Premium Luster's, and does not seem, therefor, to scatter the light the way the Epson does. It is also sharp, with as good a dynamic range (to me eye, anyway.)
I finally found how to set the margins on the roll paper to .12" on all sides. In the printer driver I set a custom paper size of 17x11. In Qimage, which I prefer to printing from CS5, I chose a print size of 10.76x16.15, which fits within the margins. I also set Qimage's page margins to "0" and that did the trick. Out came a perfect 11x17, printed to max size yet having small borders.
The idea of using borderless printing and double cutting sounded good but would require resizing the file, adding the right margins, stroking the edges, and also (I think) using all of the inks to ink in the white borders. I'd rather do it the above way.
This way, I can print 11x17's for $.80 a sheet (for paper), which is even less than buying the Ilford in 11x17 sheet size, and it leaves me free to do 16x24's on the same paper.