Usually with this type of setup, the main breaker interlock prevents the generator backfeed breaker from turning on unless the service breaker is off.Is there an manual transfer switch or something? How are you feeding the panel from the generator?
>Any issue with connecting both panel phases to 120V through a back fed common trip breaker using a pigtail? (no double lug)
>We intend to use the standard panel stickers and notices. I do not see a reason to add any but could be wrong.
What prevents someone from closing this breaker when poco power is on? They would be closing the breaker into a bolted short.
What happens if a breaker trips, someone other then the HO is looking to see what tripped, and turns that breaker on? How many non-electricians are going to bother to read labels on the panel before switching a breaker?