The skids should not make the Heli vibrate if they are securely attached and the blades are balanced both for CG nd weight. If you have the balls on take them off and try. I found the balls caused more problems than they solved. To overcome the tendancy to drift left, I permanently set a bit of right cyclic into the servo adjustment with neutral trim, then you can remove or add to it as required with the trim. While training its too hard to compensate for this left drift using the stick, you have to trim it out.
I found by using the least sensitive, inner holes on the servo horns while learning, you cant over compensate the drifts as easy