After about 400lbs/545Nm torque, stress loads are high enough to make the input shaft twist and push outwards towards the clutch. The case is then destroyed quickly.
VAP developed this robust solution which bolts from inside the bellhousing. (The transmission casing is not opened and no machine work is required.) Shaft flex is reduced and the gears are kept fully meshed together. (This saves the gear tips from snapping off under heavy torque and trashing the rest of the transmission). The tendency for bellhousing damage is completely eliminated. Since the part was installed on our 800hp drag car, there have been zero failures.
Note: Minor filing may be required, since the casing is cast, and slight variations can occur in the casting process. But again minor.