i am having a similar problem i keep scoring betwenn 550 - 570 on kaplan
and i think that they are much harder than the OG PowerPrep or any other tests. i dont think they are representative at all. and some of their xplanations do not make any sense at all especially in CR, where one would have to 'assume something' to get the right answer in a strengthen/weaken quesiton which is ridiculous since we can only infer from the premise given without any extra info that we can 'assume'. i am so mad at kaplan
some of their stuff is completely off limits for GMAT representative purposes.