Does anyone have any experience of aftermarket screens, such as Givi, on their bikes? I was wondering whether I should get one with 2 or 4 fixing points, and also what size works best (I'd like to keep the size down if poss).

Just from a structural engineering standpoint, 4 will be stiffer.

A two point mount will always have at least one free degree of freedom, no matter how tight you might make it.

Twp points make an "axis" and any force normal to that axis will turn it; the further the force from the axis, the easier it will be to move.

I get the theory, but in practice does it make that much difference? I must admit I want to keep the screen as unobtrusive as possible , hence I was wondering what actual experiences anyone else has had with smaller screens, which generally only have 2 fixing points ....