When someone at the indoor skatepark bought and tried out the Black 100s in the rebuild kit from our shop, they didn't seem half as hard as the person wanted them to be, still with some squash and significant turn, but as per other comments, if the guy had eased into them, and slowly skated them a bit more, they would have hardened up and worked.
As it was, he tightened them down about four threads in ten minutes skating and then got mad because they didn't bounce back, but still weren't tight enough for him.
Thankfully he kept them and was much happier the next week when I saw him - they were still tightened down way too much, but they had firmed up a bit more for him, or he just got more used to them, but either way they were still really hard to me and another guy who had a go on his board.
I could still almost wheelbite if I pushed as hard as I could onto one side of the board while rolling, but it was a struggle to get it down that far without falling off the board.
Thunder trucks are lower than most to start with so there is always going to be that higher wheelbite factor, when compared to some taller truck brands.