Having been involved in booking 2 of the last 4 GPs, (booking MAD) all I can say is it has ran very well.
Some have had difficulties booking for themselves and apart from getting blocked by the system after making one entry ( I wanted to make multiple entries) it's been fine.
As soon as I received a cancellation it was acknowledged and the booking in then allows someone else to book.
I must say though that at GP2 MAD, I had quite a few who cancelled on the day at booking in which did stop some shooters attending and shooting. Not on really!
Your efforts and time making this work are to be congratulated. You respond within the hour if not immediately.
Maybe a list of perpetual no shows needs to be worked on and then maybe they can't book on line? Harsh but then these shoots do fill up rather quickly.
Thanks for all your help