I recently got my daughter the Langes and professionally fitted. I put her booster strap on and did a little surgery (shaved down the sides) to get it to set under the shell. While doing so, I noticed what appears to be a cut line on the upper shell flap approximately where the red line is drawn. I'm guessing it is there in case you need to remove it so either the original power strap or booster strap can lay flat. With the booster strap under the shell, I notice the cut line is actually above the top of the booster strap. My thoughts are that since the cut (red) line is above the strap, it is going to be annoying either getting in the way of her race suit or making a shelf to accumulate snow.
Not her exact boot. Just snagged something off the internet.
My gut tells me to cut it off. My experience tells me to ask first.
Appreciate any insight.