The 9860 STS already has a 12.5 liter engine so, I doubt they'll go smaller since the 12.5l's replacement is a 13.5 liter Tier 3. A wider feeder house will likely do little to improve feeding performance and efficiency into the FAST system and rotor (example, a 2388's feeder house width conforms to the diameter of its rotor intake to achieve optimized feeding, same with the NH's FH relative to the distance between the opposite outer diameter between rotors). A Axial rotor combine's feeder house needs to stay as close to the diameter of its intake housing as possible to be efficient. It might be that the feeder house gets a little longer to improve visibility. A larger diameter rotor is going to take more power, won't work well if the engine goes to a smaller 12 liter ;-) As for cleaning capacity, the only room for an STS cleaning system to grow, given no changes to the frame and chassis, is in its pre-cleaner. What will a larger pre-cleaner do?