My operating limitations only require me to notify the FSDO of any major change per 21.93 and wait for a reply.  In FAR 21.93 a major change is defined as <>
I used to believe the definition for 'major alteration' as defined in 43 App. A was applicable, however in the applicability section (43.1) experimentals are specifically excluded.  I also spoke with my insurance company, Avemco, who told me that as long as the FSDO was happy, they were happy.
So the bottom line is, know what is in your operating limitations and talk to your local FSDO.  They can all be different.