I run the double stacked helicals all the time. I have heavy duty loewen concave,with the heavy arms. n of filler bars depends wheat,durum and flax usually two rows,Barley one or none depending on volume of grain in swath, canola and SF none. I have removed cage sweep and installed a blockoff panel next to l.H. concave arm,seems to eliminate buildup there. last year I had Russ HRSW myself and combined lots of that along with Gunner and Pioneer 2375 on my custom jobs. Russ and Gunner were tall and 25-40 bpa lots of straw.Pioneer 2375 is threshed by the feeder chains I think! I normally run an air foil chaffer on all crops but last couple of years I've been putting Std. chaffer back in,opening it up and running wind higher 6-7, in wheat only to reduce shoe loss.Concave is in with 0 wedge, bars are black loewen bars,on original rotor.I have 4 seasons on them and may put chrome ones in this time. With the yields we have in NC North Dakota on wheat and durum, rotor loss isn't much of a problem as long as concave is threshing properly.I really keep an eye on accelerator rolls as they seem to vary in longevity, I think certain crops and weed seeds are really hard on them.I have a friend who put a double belt and a smaller pulley on impeller to speed it up and he really liked the results. That will be on the list for pre harvest. My local mechanic is a guy by the name of Ray Rhame, maybe some have heard of him,his knowledge of Gleaners is amazing. He has helped me get my 16 year old machine to the level it's at. Sorry for being long winded, I didn't get to talk snowmobiles much this winter so it's back to combines.Hope the wife doesn't shoot me! later John