Okidata Custom Size Forms w/QuickBooks

I am trying to print to a custom sized form 6in wide by 8.5in high from
QuickBooks 2005 and XP, to Okidata Microline 321. I went into
Start-Printers and Faxes screen, did a File-Server Properties menu
option and defined my new page size as 6 wide by 8.5 high and named it
appropriately. Then I went into the Printer's properties and assigned
the new page size to the printer. I printed a series of test pages,
all of which honored the new page size. Then I changed Quickbooks'
printer selection for the given form to the printer I just set up, and
made sure that I selected the option to use the settings assigned to
the printer itself, but the printer still printed as if it was printing
to 11in paper. In QB, I did not see my new page size available in the
page size dropdown. The fact that I can print test pages correctly,
tells me that the printer is set up right on XP, but QuickBooks must be
forcing some other parameters to the printer regarding page size. The
custom page size options in QB are giving the error "The selected paper
size is not supported by the printer. You must modify your paper size
selection before you can continue." This printer is being used by a
DOS program currently, and the program seems customized to print to
these forms. But if I could find a printer driver that would work with
Okidata 321 that already contains a paper size option for 6x8.5in,
maybe QuickBooks would be able to work with that. Does anyone here
have any ideas? Thanks in advance for your help.