Which statistical tests are you going to use? What degree of bias are you trying to exclude? What p value are you happy with? How many rolls does that require?

This method has always "felt" like the best way to turn dice rolls in to bits to me, but I am not a cryptographer and I'm not ruling out some bias which I am unaware of. Which is why I always recommend that people don't come up with their own ad hoc schemes.

It will be far quicker using a Von Neumann approach to flipping a coin to generate a provably random stream of bits than it will be to even begin to test the fairness of your dice.