Hello,
I spoke with stefanct on IRC today about using flash chips of 32MB size to store a small Linux installation next to coreboot. Apparently he will work on support for 32 bit addresses needed for chips > 16MB during his GSOC and he told me to write to this email address and he would give me a definite answer after this summer.
Furthermore I've attached the log output when reading the flash of my board (Asrock E350M1/USB3), maybe this can be of use. From reading the specs, the highest capacity chip from Winbond for "PDIP8 300mil" is the W25Q128FV. There is a 256Mbit version, but only in different packages.
Mh, a cli-only system should fit in a compressed 16MB ramdisk, but adding X and a browser (midori) would already be a huge challenge on 32M.
Anyway, I hope your work will succeed.
Good luck,
Johannes