Just a word or three of caution to those new to this...
By "practicing" beforehand and getting some time on the aircraft (like the Grob) before the assessment, you are raising the bar for yourselves. What the assessment officer tries to establish is how "trainable" you are.
By being familiar with the aircraft and procedures, you raise the level that you have to improve on. If you are familiar with flying training, you would know that the largest improvements are most often shown at the beginning of flying training (exponential) and then the curve (rather rapidly) levels off.
I'm not trying to rain on your parade, just advising you that you may be trying to be TOO smart...