I'd hire a boom mower for the first time and find a used sickle bar mower, 7 or 9 foot bar, and run up and down once a year with that.
I've been searching for a sickle going on 3 years now. They are just tough to find in my area. Finding one that operates from 0 to 90 degrees AND has parts available at a reasonable price seems to be a needle in a haystack.
I keep seeing the county tractors trimming along the roads with boom flail mowers. I'd love to offer the guy some cash to make a pass up and down my driveway, but I don't want us both to wind up in jail.
ac