While initially the size of holdings matter to get it above 5%, once that has been achieved (and by the sounds of things it most most definitely has here) I think sheer volume of names is a priority, regardless of holdings size - provided of course its manageable for the organiser.
The number of shareholders in these sorts of groups and supporting the actions will be what media picks up on.
Then of course it’s good to have a hidden/undeclared big block of dry powder in reserve to push things through when things come to a vote.