An idea for practice: the manager can choose the litter of each turn.
For example: take one 45L, one with 40L, another with 35L.
With this, you can imagine the impact of making a leg heavier or even making a pit less.
Remembering that the return to classification is made with the ideal fuel.
And practice tests would have no effect on classification.
Why not reduce the practice sessions to 3; but allow the car to be filled with a certain number of laps, and provide something similar to what you can see after the race of the race data.
This way you can still find your setup, but then you also get a full stint worth of data.
This for me closer replicates real management of a race team where you get 3 practice sessions and a lot more data than just a PL5 no fuel time.
