I can think of a couple of things to look for:
Check the lateral balance. Hold the nose and the tail of the plane and see if one wing dips. You may have one wing heavier than the other. If this happens, add some weight to the wingtip of the other wing.
You said everything appears to look OK. What exactly do you mean by everything?


FYI, it's easier to read questions when they are not in all capital letters. FOR EXAMPLE, THIS IS NOT AS EASY TO READ AS THE FIRST PART OF MY REPLY...