Our slope that he mows isn’t very big. More of a patch than anything, maybe 10’ x 12’. It’s not dangerous how he does it. I think yours sounds like a bit more than what we have.
Here's a pic ... part closest to the camera is the part that has not been done (good samaritan weed eater guy ran out of gas). The bank does not look that steep in the picture - very deceiving. Near the bottom in some places, it drops off almost straight down.