I run a R-62 with 8 row head with square tooth chaffer,will push it 4.5-5 mph in 200 bushel corn.I don't think you loose a whole lot in capacity,but you do loose a slight amount.Apples to orange comparison,had a M-3 with 4 row head and round tooth chaffer,could run up to 5.5 mph in 200 bushel corn.