Operate off anything else and run into the trees at the end the Feds are going to ask "how did you substantiate the take off performance?
This is what it really comes down to, and post after post has been skirting round this reality.
Here it is again:
Run off the end of the runway due lack of performance and CASA will come after you. The proof is self evident. Outside the charts or not, you have demonstrably taken off overweight.
or
Get safely airborne and CASA will not come after you. Sure, somebody may dob you in because he knows you were outside the performance envelope, but even in this case, CASA would think twice about whether it would be worth pursuing you.