Originally Posted by
Check Airman
I’ve been 900ft below max (can’t recall if it was a 200 or 300) and thought the buffer was sufficient.
The reference you will find in the FCTM is related to maneuvering. Can't recall the numbers for the 777, but in general Boeing asks to limit the bank angle from 10kts above maneuvering speed (amber band). It's not the straight and level flying that is the issue, it is the banking and maneuvering.
Set the correct cg, limit the bank angle and you should be fine (ico turbulence you can always ask to descend if really necessary). Depending on how long you have to go and the local ATC environment, I've been 500ft below many times to avoid discussions further downroute (first come first served idea).
I've also been 100ft above, but that's a long story involving Chinese ATC with altitude restrictions at the entry waypoint and a subsequent unexpected speed restriction. Didn't feel uncomfortable, apart from the need to go into HDG SEL and limited bank angle.