If your wing had a 20mm hole in it, you would loose lift, and it would start creating drag.
The best game IMHO for you to "feal" the damage, is IL-2 or Janes ww2 fighters.
If you so much as take a bullet hit to the wing,your plane will let you know it by "feal".
Im sure its all just a matter of "when we get to that part" for hitech, im sure there working on the graphic parts first, then if they wanna add "0.3- lift" for a 20mm hit, or 0.1- lift for a .50 or .30cal bullet hole.
but then YOUR computer would also be sending much more "im wounded here, and here..and here" packets to the server, so everyone would "see" your bird flyin' all funky.
part of the reason it is so easy to land damaged rigs, is besides looseing MAJOR body parts, little damage like tears, holes..maby even bent wings from max speed diveing .ect have NO real effect on how the plane feals, and flys.
All in good time, im sure.
then we will be like,WRAAAh i got hit by a 20mm in my 109's wing now i cant go under 250 or im going to loose half my climb rate, and start auto rolling like crazy or whatever.
anyhow, my two cents.