You should be able to at least duplicate what your R50 was doing plus. Steep thresher helicals will help prevent straw from running over concave a second time, rotor sweeps will help prevent any grinding of straw on seperator side, try running no reverse bars, make sure bars are at least extended to area ahead of discharge. Retract chopper knives. If that isn't enough I have heard of guys running chopper at corn speed. At least one guy running a pair of 65s with hydralic spreaders have set electronics for a minimum spreader speed of 50RPM and he says it make a very nice straw windrow. He has basically the setup mentioned above but can't tell you if he has fine cut or normal choppers. I don't think you would have room for a removed cylinder bar on seperator grate for they would be to tall. I wouldn't worry about a stationary rasp on belly especially if your looking at a '97 or newer machine with adjustable seperator grate. I don't believe the adjustment of seperator grate will make any noticeable difference in straw quality.