On the whats and whys posted herein, I back when 5x6s were king around here, 1600# was the top end benchmark...if you made that you were the top 1%.
Based upon that, with all things equal I did a little Algebra and came up with this based on size variances alone:
5x6......1600 What my JD 530 might do.
5x4......714 What my current JD 375 might do.
4x6......1280
4x5.5...1083.....Tx Jim, you said yours went about 1000# for that roll......right on bro. Grin
4x5......886
4x4......566
So for the buyer, where hay is sold by the roll, it makes a big difference in the diameter as what you get for what you are charged.
Seems net wrapping and 4x? is what's baled around here currently. Farmers bail 4x6s for themselves and sellers 4x5.5s; both dimensions understandable for the circumstances.