have you performed a vcut surgery? the only reason you would cut the back of the boot is to make it move freely. the back of all ski boots is made up of plastic that binds together to STOP flex or "tilt." the front of the boot actually flexes, so when you put your booster strap on you can only flex as much as the back of the boot will let you. if your following so far, youll understand that shin bang comes from the back of the boot not flexing the same as the tongue will allow. when you cut the back of the boot the boot top and tongue can move in sync hence changing the flex pattern and integrity of the boot to allow more bending which inherently allows things like ollies, presses, and Rollerblade grinds
some people know things from experience not from reading forums.