I never used any of the forms that came with my secondaries and none of the schools asked me to after they got the form I used. I did use the form that my undergrad pre-med advisor gave me. It had a bunch of things that they could rate me on and then had a place for them to write comments. It also asked me to sign if I agreed to waive my rights to see the form.
So you can get away with not using a school's form but make sure they address the same things that a secondary would ask about. Do you have any old secondary forms so you can know what the schools want to see? Some just ask about you in general, some ask if they know how you handle stress, some ask about your devotion to the medical profession and ask if you can handle medical school in their opinions, etc.....
