Are you proposing to also make the form bigger when the controls grow?
What will happen when the form is bigger than the screen?
Sometimes you have to put a limit on things.
Try sizing a control for one of its items and, when you fill the control with content, resize the control to the lesser of (minimum) the number of items AND a reasonable limit. That way if the number of items goes over the limit the control still grows a scroll bar. EG the control will grow for 2, 3, 4 or 5 items but from then on it stays the same size and shows a scroll bar.