The doubling of fixed costs was to estimate a full year of fixed...

The doubling of fixed costs was to estimate a full year of fixed costs based on the published half year of fixed costs. Cannot really see that being too unreasonable.

The cost of production is what leads to the 46% margin. Those 'variable production and direct cost of sales' related costs have been treated separately. They are not doubled but flex with sales. Extra sales generate an extra 46% margin to cover the fixed costs.

I have not estimated the marginal cost of additional production (because I just can't) but it is unlikely to be materially different to the 46% (taking into account the balance of volume discounts, production overtime, production efficiency, despatch efficiency...) so I don't think it would change the big picture.

So, appreciate the prompting but it hasn't made me really alter the sceanrio. I am not saying I am right but simply want to test whether its rational.