You could just expand the rom file to 16Mbit with FFs and burn the resulting file.
EDIT: With a hex editor I mean
i am using the tl8766 plus with the 27c322/160/800/400 adapter usually i cut the rom files in 512k chunks and i flash it once per time switching banks. in that case can i flash only the first 2 banks and left the other 2 banks empty or i can flash them twice in the 3rd and 4th banks?
it is what i have done but i had to cut to 512 to flash them with the tl866 plus adapterIf you connect the high address pin to ground, you should be able to use the low-half only. But... it's more convenient if you just burn the image twice, so the high address bit doesn't matter.