Try trimming an outer row of pins off at the front to help curb grip roll. Also try a thicker anti roll bar, and thicker shock oil.
Mike at RC-Monster makes a 'Slipperential' which is a slipper clutch built into a centre differential. Unfortunately, it won't fit the Hyper 9E, as the centre diffs used are the same size as the Hyper Mini ST, not normal 1/8 size. Also, try better threadlock; a lack of a slipper is nothing to do with loose pinions.
Worth a look as far as set-up is concerned is the Hudy set-up guide (try
here)