Any cinnamon fern gurus out there?

I know that growing conditions play a big part in how large a fern clump will grow but in general terms how large should an 8 to 10 year old cinnamon fern be?

I needed something rather large to use in a shade bed; I just happened to be perusing the fern listing on e-bay and ran across a listing for 5 'HUGE' cinnamon ferns. I only needed one but figured that hopefully I would get at least one fairly large rootball and the rest even if they should be smaller could be used else where. I contacted the seller and asked how large the ferns were, I explained that I needed very large ferns to fill in a shaded area. The seller replyed that the ferns listed were 8 to 10 years old. Of couse I knew better than to expect much but these ferns don't even come close to 8 to 10 years old. The largest is just slightly too larger to fit in a gallon pot. I know, I know, I should have known better.