You do understand that some complete stranger is going to open your throttle and rev the balls off your car consistently for 40mins or longer?
You've already been told that there is no-one in Scotland who knows the zed well enough to tune it effectively - so why would you trust any of them to stick it on a rolling road to even measure the outputs?
What are you hoping to achieve from Saturday? Where will they be taking the readings from? How many zeds have they worked with before? Have you even asked yourself these questions?
Only trying to get you to think things through....its your baby after all