Which rolling basket on an Excelerator preforms the best, round bar or flat bar? Will be using in fall and spring standing corn stalks. Could possiblely be using in bean stubble in the spring. Very few rocks in the fields. Please state why you like one over the other. Soil type is silt loam. Also what size of Excelerator for a JD 8420 in fairly flat ground at 8-9 MPH. TIA