The Final Battle had N allied fighters, 0.68N allied bomber aircraft, and 1.59N axis fighters.
Right now, we have N allied fighters, 1.84N allied bomber aircraft, and 1.23N axis fighters.
In other words, if we ran The Final Battle again (where Lancs did at times make it to target and where they didn't get all destroyed every mission) and increased the number of Lancs by a factor of two, and reduced the number of axis fighters by 22%, how would it go? Wouldn't the Lancs do better? Well, that's what we have in Fjord Fury right now compared to The Final Battle.
If you have a scenario with N allied fighters, 2N Lancs, and 100N axis fighters, all the Lancs will die every time. If you have a scenario with N allied fighters, 2N Lancs, and 0.1N axis fighters, all of the Lancs will live every time. Somewhere in between lies balance.
We want a balanced scenario, where it's not a cakewalk for the Lancs, and it isn't 100% loss every mission.
So, what do we put in, and how do you estimate that is the appropriate number? I am just going by past scenarios and tweaking from there.