Sport cub s problem
 

my Sport Cub s Dolphins when in intermediate or advanced mode. Can anybody give advice on how to keep it steady and not go up and down all the time ?

Is it properly balanced and trimmed? I have one and if you're not over controlling it and the balance is right it flys like a dream

I have just come out of beginner mode. I have tried to place the battery in different spots. The trim is about neutral. I flies good in a turn just goes up and down when straight.also flies great in beginner mode .

It sounds to me that it is PILOT error . Reread your own last statement. I would suggest a little less pressure on the sticks and an attempt to smoother flying ( stick movements ) . Red

Yes you are leaning on the gimbals(sticks). Common problem with folks when learning to fly You need more practice out of the SAFE flight mode and you will hopefully develop good stick control.
It takes time but you need to break this habit . Once you pick up bad habits you will have a hard time getting better at flying.

Maybe try a little expo on the elevator?