I have a set of reissue rat bones 90a that I can powerslide on. I have a set of 90a Oval Dragons that I can't powerslide on. Strange! I also have a set of black rat bones 2 that are 97a and a white set. The black ones seem harder and slide better than the white ones. Strange! Anyone else notice this? This is not meant as a complaint, I love all bones and powell wheels. They are the best.
You can't powerslide the Oval Dragons because 90a is pretty soft, there're not meant for that. As for your Rat Bones maybe one of the sets are pool formula.