You will need a larger trimmer with heavy trimmer line .155 or so will do great. I use a fixed line head for this without a guard on a FS130 but a FS250 would probably work better. BTW I have a few of these types of jobs and this has worked the best. After your first Spring trimming you may be able to get away with using the FS100rx if it will cut it fast enough for you, that's what my guy does when working on these projects. I would skip the idea of using a heavy grass blade as mine was a waste of money for what I was working in.
I've never been skydiving, but I have zoomed-in on Google Earth really fast.