>Trial and error. I enlarge the form until I've got no more problems. You must also leave the right part free of controls.
>
>I've got frustrated by this behaviour (smell like a bug to me), that I've given up on srollable forms and used pageframe instead.
>
>>I tried that. I made the form width 16 higher than I wanted it to be but it still changes with each modification. How did you get yours to stick?

Don't give up on it. This is a bug. What I did was determine the initial width of the form I wanted, then put that setting in the form's INIT [This.Width = ###]. This does not help during design, but I just widen the form to an arbitrary width and not worry about it since I have the correct width in the form init.