I'm not against anybody playing or experimenting. However, I don't think you understand fully how the needle works. There is a certain amount of travel. When you twist the throttle, there is only so much movement. certainly this is more than 5mm. but for the progressive transfer to happen, everything must take place in a small area.
Once again, feel free to try. I would just believe instead your current tune is not right. If you are fouling at 1/2-full throttle, then it's your main jet that should be the culprit.
Is your bike new, or new to you? Is the carb stock? Is the bike stock? Is your ignition in good shape? are you sure?
There are a few really good discussions on reading plugs properly. It won't take more then a few mintues of good hard riding to be able to read a plug. Make a jet change, or plug heat range change, test again, repeat.. You could have your bike good enough to have a plug last longer then a day.