Not a really a question - more a tip.
Don't make the same mistake I did! In Board 11 you are able to restrict Selectors to one member. If you want to make this a permanent change to the screen for all users, then make sure you check the box in the Selector settings over to the right of the screen (highlighted in yellow below), then save the screen changes. If you check the box shown in red below then the restriction to select a single member only is only valid until you leave that screen (even if you are in Design mode).
Once you have checked the box in yellow (and saved), the option on the left is greyed out, as you would expect: