Take a proper screw driver and only loosen the screws surrounding the top case... try and see if you can level out the top case a bit so that its flush, and then tighten them down... but dont tighten them too much. Oh, and make sure you are on a level surface, cause you can tighten the screws down and have only three feet touching... while amusing... its not good.
Sometimes they can over tighten the screws and cause the case to warp slightly.
If you feel uncomfortable doing this, then dont do it... but I found my case originally was tightened too much, and just relieving the screws and allowing the top case to fall back into form again helped a lot. Everything is nice and snug now.