v  To determine the minimum bottom margin, subtract the length of the     custom form from 355.6 mm or 14 in (the maximum form length). For
    example, if your custom form is 300 mm long, subtract the custom form
    length from 355.6 mm (355.6 mm - 300 mm = 55.6 mm).
    Your application would then apply at least a 55.6 mm bottom margin.
    Again, note that the minimum margin prints to the edge of the paper. If
    you want to leave additional space at the bottom of the page, add it to
    the minimum.
v  For the top margin, use whatever value you would normally use. No           special calculations are required.
3.   Always run some test prints before submitting a large job. Chapter 4. Paper Handling 53