We have been using the No-choke Crary guards and the Crary spring hold downs on our 30 ft 500 series flex header. The knife is a standard AGCO knife with double cut sections. We have used this combo for a number of years in lentils and small grains. In small grains we have less head losses from heads being cut off and springing forward in light crops, using the double cut sections. The double cut section knife is heavy driving but a lot of potential problems with the knife, knife head and wobble box are overcome by smoothing out the drive by installing a fly wheel on the wobble box. [ Hyper Mods ] The flywheel with it's greater inertia gives a smooth, steady drive and greatly reduces the stop, start shock effects on all of the knife components. We had a situation in green lentils where a knife bar with the double cut sections broke [ after some 4 or 5 years of operation ] so we installed a new standard section knife we had on hand. We harvested for about 300 metres with this knife. The job was so ragged with bad losses that we pulled out and replaced all the standard sections with the double cut sections. All was right with the world again! Can't comment on the SCH as we have never used it.