I didn't get a picture of my wing before I sheeted it []. That picture was from another club members similar plane, but I used a very similar cutout pattern with identical results. It really does lighten the wing quite a bit. Believe it or not, the foam is not the least bit flimsy.

Yes the cut-outs are hotwired. I just added a long thin metal attachment to my solder gun, nothing fancy. The big thing is to think carefully and make sure your cutouts will not interfere with anything (wing tube, servo mounts, etc). I made a template with the cutouts to lay over the wing, then marked them in with a Sharpie. Remember, the wing still has to take an enormous amount of load in the maneuvers we put our models through. After that it's pie if you have a steady hand.