One point I would emphasise is that local knowledge and experience is required to make the sensible decision about extra fuel. If you fly the same route regularly you get a very good feel if more is required. The Plog plans for the shortest departure and for the longest approach. In Munich flying the whole transition requires several hundred kilos more fuel. Most times on arrival it is not required and is therefore effectively extra. On the other hand going to the Canaries with Plog fuel might not be the wisest decision.