No damage at the walls at all, at least nothing that I can see (check pics) with that piston as low as it goes.
Yes, my car was a twin turbo car, I drove the car from Chicago to DC, drove it around here with 10psi it drove perfectly and then I took it to a shop to have them move the power to where my class allows ( the rules go by weight/rwhp) and in the 3rd or 4th pull... the piston let go. They shot down the car and then I took engine off the car.
To be honest, when I sent the pictures to Ford, they said that they would change only that piston because of how good everything is and how low miles the block has. As I stated in some PM's, I'd put stronger pistons... just in case you might want to go wild later on.