printing checks on an Epson LQ510 in Windows NT

I have written a program in Delphi v1.0 and it prints checks by using the
User Defined form for an Epson printer.  In the contral panel you can
change the height and width to 350x850.  Then, in your program you can
set the form through the device mode.  

However, in NT, even though I can create a custom form type I cannot see
the form definition in the print manager of NT.  Does anyone have an
example of how to affect a custom page size in NT?  I am especially
interested in using Report Writer.