I am installing the OAK for my new Harman XXV. The OAK manual says to set the OAK opening to 2 for the XXV, then cut the insulation. Everything seems ok, however, before I make the final cut of the insulation, I just want to double check. It seems that changing the setting from one number to any other does not reduce or increase the actual opening in anyway. Is it just my imagination? I rotate the adjustable setting back and forth from one different setting to the other there seems to be no change. What is the actual difference between setting 2 and 7? Can anyone please enlighten me before I make the final cut? Thank you so much.