So I have a normal skinny poly new-work side mount fixture box on a cathedral ceiling, the ceiling right there is roof sheathing direct on rafters direct on drywall, so no attic access. It's up to 34 years old and I expect not fan rated due to the thin walls, it doesn't look like the fan rated ones that are usually twice as thick and I don't see evidence of the typical nail on metal support brace that extends up and is found on at least modern versions of the poly side mount fan boxes.
I am putting up a ceiling fan so my thought is to surgically cut next to the rafter and snip both nails holding it in, allowing me to turn it on its side and pull it out of the drywall hole. Then I plan to mount a fan-rated saddle box two inches over and conduct the drywall repairs on the "half moon" left over from the original box location shifting over two inches.
This seems to be the easiest way I can get a fan rated box in there since I have no access to put a support rail or 2x4 in without major excavation, any other thoughts?