I would STRONGLY recommend that you stay away from "practice" in a rented 747.
The sim ride is heavily weighted (60%) and is pitched at the level you are initially assessed at. If you practice, you are setting the bar that much higher for yourself to improve as the session progresses. You are expected to show an improvement from beginning to end of the session, so if you start at a high(er) level, the efffects of a slowly levelling curve (as any experienced trainer will tell you) will start to tell.
Don't do it. Do NOT rent time in a sim to "practice". You are making it harder for yourself and wasting your hard-earned money.
NO NO NO and again NO