If I remember correctly, Oliver claimed the jointed disc style coulters produced less draft than the straight coulters with coverboards. All I know is that I could pull a 5 bottom 575 as almost as fast with a 1650 as we could a 4 bottom JD with coverboards with a 4020. With either the old style round coulter shafts or the newer flat iron type coulter mounting system, make sure the coulter spring is adjusted paralell with the frame members of the plow. This makes a huge difference in the quality of your plowing. With the round shaft, you simply loosed or tighend the front or rear mounting bolts to adjust the coulter. With the flat iron system you shimmed the front or back of the flat bar to line everything up.