For what it is worth -

I purchased an used experimental glider in November 2014. I dutifully sent in my program letter to my local FSDO in January 2015. Later that month, I received a phone call informing me that because the glider was changing "home FSDOs", I needed a new Special Airworthiness Certificate and Operating Limitations issued by my local FSDO.

The FSDO was great to work with and the process went very smoothly but, it was required before I flew the aircraft.

Lou