I have combined these two requests in a single ticket as I feel that they are closely linked, and the second does not make much sense without the first.
Stretch option for Gantt task visualisation
It would be very useful if the user could specify a 'stretch' option for the horizontal width of the Gantt which causes the task visualisation to fill all of the available space (by increasing the PixelLength). The Gantt chart looks very strange when a fixed PixelLength results in a large amount of empty space, particularly as most other containers can be resized. It can also be difficult to guarantee that the Gantt chart fills all available space when it is inside a resizable component.
Ability to move resize control when both sides are at their 'desired width'
Currently, the resize control which separates the column data on the left from the visualisation of the gantt tasks on the right cannot be moved when both sides have reached their 'desired width'. However, this is not intuitive as other types of Telerik controls (notably the GridView) allow the width of components to be increased or decreased by clicking and dragging left/right, even if an absolute width has been set in the XAML.
I recognise that these features may not be desirable for all users, so it would be helpful if these were features that could be toggled on/off.