Ive added this to hopefully solve some confusion about the icing in the game.
There is visual icing (the model you see) and structural icing. These values are connected, but also not.
The structural icing is what actually affects performance. You can be 100% visually iced up, but structurally 0% and have no performance hit.
The visuals are sadly rather bad at showing this. The leading edge shows that, instead of the whole wing and tail surfaces.
So yeah, ive added this popup at 50% structural icing to give you feed back that the plane is icing up, as this is a sim and you have no feeling over the plane.
This is partially true to the real plane. If there is a large amount of ice build up, the pressure can be high.