I've been very impressed with the R42 and R52 in corn, provided a couple things are done. These machines should have every other wire pulled_cut out of the separator grate in order to utilize the effectiveness of the reverse bars. 2 normally work well. The concave should be looked at too. The spacing, wire center to wire center, should be about 1 1_2". If it's narrower, every other wire can be pulled here as well, especially in corn. It sounds like you do some wheat too, which might be a possible problem at the concave. You might be able to use enough filler bars to compensate for the wider wire spacing, but I think what I'd do if you have to pull the wires out of the concave and want the flexibility to do wheat and corn, I'd pull them out of the rear concave section, and leave them installed in the front section. Should allow you to thresh the wheat well enough, while giving you much more separation capacity in corn. And if you need to put the wires back in the rear concave section for wheat, it is pretty easy to drop the concave wide open inside the machine by disconnecting the linkage. To your other point, yes, the R65_62 is a lot more forgiving than the R42_52, but with a bit of time, the R42 is an amazing machine, and you'll have more $$ in your pocket.