We ran the Estes Disrupters (qty 9) in the rear grate for a few years which did a nice job of grinding up the straw when it was dry. However, we didn't like the power in took and in damp straw there was little effect. To be fair, we didn't have the spiked bars on the rotor. last year we mounted 4 sickle sections in the back two grates to hopefully cut up the straw with less HP. It worked to some extent, but I think we will run 12 of them this year, four in each grate. I've considered the Shark Tooth Grate a few times, but have not tried it. For my $, I like the chopper fitted with the aftermarket sickle sections. It does a real nice job, but it sure is hard to justify adding one to an old machine. Mike