When a flow break is configured on adjacent controls within a FlowLayoutPanel, the Width computed size returned by PreferredSize can be incorrect.
In the simple case where a flow break is placed after EVERY control on the panel (i.e. one control per line) the computed width is ALWAYS incorrect.
In that case the preferred width returned should be equal to the widest control (plus any margins). However the returned value appears to be the width of the widest control PLUS the width of the control which will be placed on the next line.