We have a 2388 that has the Mauer extension plus the 6" tiptop on top of that. Holds around 320 bu corn. It also has a hyd powered bubbleup auher in the tank. This is our 2nd year running it and so far have not slipped the clutch. You're asking the fountain auger to push a lot of grain up to fill the extension. As pressure increases you are backing corn up against the elevator causing the slip clutch to slip. The bubbleup auger eliminates that problem by taking a lot of the load off the fountain auger . Money well spent IMO.