Hi Jill,
I believe the problem is going to lie somewhere in the "lines" values for the form. Most printer forms are better defined in terms of lines rather than inches. For instance 8.5 inches is with most standard size (12 pt.) typefaces equal to 66 lines. In some printers you must "fake out" the driver by making the page length equal to 60 lines.
It sounds like you have one (or more) too many line in your form for the current version to print "right." Try taking a line (empty) out of the form (just as an experiment) and see if it "crawls" or drifts. One too many lines may not factor properly for a height of "4.25" without making the form print "long." To test, place a dashes of dashes (---------) on the first line of the form and the last line of the form. This will show you where the form "really" exists which is sometimes hard to determine. Any constant element will also do without modifying the form.
I should also mention that a printer form parameter you might want to investigate is "print over perforation." This pertains especially to the continuous feed forms--which multiple checks on an 8 1/2 X 11 sheet size are if you are using something like VersaCheck stock--have this parameter so that it does not have automatic top and bottom margins.
Hope this helps.
Dick