Its deffo the 11th and 12th, i do my usual of phoning the hotel events team and asking, just saying i'm part of set up team and been given 2 dates etc, can they confirm.
As its expensive enough booking the trip so early booking is best.
The guy on the phone confirmed its the 10th for setup and sat sunday is the event
The main issue is if the painting comp is on the sat or the sunday, as they have mucked about with this recently.