Ann: Half Yearly Report and Accounts, page-14

sox recovery will never be as good as sulphides but the high grade of the ore should be able to compensate for reduced recovery.
the dewatering cost is significant but fixed. It's higher because they are also reducing water levels to mine deeper as well.
The system itself is very large and produced for decades previously - so this can turn into a significant cash flow generator if/when they get it right and there is ample 'headframe shadow' exploration opportunity as well.
Zinc price strength can't even seem to breathe any life though so perhaps your assessment is right.
price action would indicate another disappointing quarterly coming up