I mow probably 300-400 acres a year with an 8' cutter.
Where I live, (wife's family farm, about 250 acres, maybe 50/50 woods/fields?)
I used to cut the place with their IH 444 and 5' rotary as her father & uncle were getting older and unable. Finally, I decided one summer that living life was more interesting than spending nearly the entire summer cutting "their" land (which my wife now owns part of so I wasn't blind to that progression) AND, I paid for the fuel to cut their land.
(I'm such a dang good son-in-law)
I finally stopped cutting and miracles of miracles, a year later, an International 980 shows up with a 10' HD Rhino mower! So now I can get moving.
Father in law passed and his son sold the IH and Rhino (never asking if I might want to buy it from the Estate)
So given that I live here and now we have NOTHING to cut the place with and not wanting to rely on any tempermental family members, I bought my own IH-1066 and a 15' flexwing.
Now, if I bust my hiney, I can cut the entire place in a single day OR, I can be more casual about it (I enjoy cutting the fields) and do it over a couple days.
I've got to agree....can't believe that you're not using a larger mower. I've been considering getting a 20' flexwing.