Yeah, I always wondered why JD introduced the 24" diameter rotor in the lone 9560 STS. I suppose it does give them a mass market evaluation of the benefits of a smaller rotor, greater Fc, Centrifugal Force versus the 30" diameter rotor in the rest of the STS line. Also lets them compete directly against the Case 24" rotor. It might also be nice to have the 24" rotor in the parts system if they wanted to build a rotating concave cage _ bi-rotor around it and stick them incognito inside the 9660 and larger STSs. That would make worldwide field testing much easier. Pretty slick move on their part.