I did mine without an SF97. Its a 1952 so I told em it has had who knows how many owners. I tried doin mine just in paperwork, but they told me they needed to see it. So I brought it in, and just about every clerk in the office had to come out and look at it, they didnt know what numbers to use for the registration. I finally stopped them and told them to use the serial number on the data plate. My trailer has two plates welded on the tongue "A" frame, they used those as a secondary. I was lucky, I told them I wanted to use the Calif program YOM, Year of Manufature, so I could use 1951 plates with a 1952 registration tab, and they did that along with the Perm trailer. 56 bucks every 5 years!.
Nick