The "base unit" I worked to in terms of sizing was a large tin of evaporated milk...410g instead of 170g. This meant that the batch would be roughly 2.5x larger. There was also the weight of the cocoa powder (quite a bit of it!), so I expected 14-15 portions of ~90-100g. It's interesting to note that the dry weight of this recipe was 1.5kg, however the final slab weighed in at 1.25kg, so there is a loss in weight (almost certainly moisture loss, with a small amount of mixture lost on utensils and bowls) of ~15-18%...good to know if I ever do a larger batch (I'm limited by tins to set the slab in I think...). I did each portion as 90 grams, and I planned to do 14 portions, so there is a nice round 200mg of caffeine in each portion.
I have a spreadsheet I use to work out basic calories/nutrition values for recipes. This one comes in at 388 calories per portion, which is a little on the heavy side! It is nice to be able to print a little label with the headline numbers on though (not that it stops cyclists consuming everything in sight...). I have tweaked the ingredients to reduce the costs as well (things like granulated sugar instead of caster sugar). 
Fast Fudge V2 - Recipe
- Line a 30cm x 20cm Swiss Roll tin with baking parchment
Ingredients
- 410g Evaporated milk (1 large tin)
- 725g granulated sugar
- 120g butter
- 100g cocoa powder
- 70g golden syrup
- 120g condensed milk
- 2.8g caffeine powder
1) Place all the ingredients in a large, heavy-based pan
2) Put over a low heat and stir until all ingredients are melted
3) Turn up the heat to medium, and continue to stir
4) Monitor the temperature while stirring...heat and boil until the temperature reaches 116'C
5) Remove from the heat, and whisk until the mixture thickens and loses it's gloss (I used an electric hand whisk for this)6) Pour/scrape the mixture into the prepared tin, and level the top
7) Allow to cool until completely firm.
8) Chop into cubes, and separate into 14 portions (each will have 200mg of caffeine)