Hi Eric,
Thank you for using Syncfusion products.
You can use SetOuterDockAbility method instead of SetDockAbility. The following code snippet is used to dock the control only to the right.
[C#]
dockingManager1.SetOuterDockAbility(this.panel1, Syncfusion.Windows.Forms.Tools.DockAbility.Right);
Please refer the below sample that illustrates the same.
http://websamples.syncfusion.com/samples/Tools.Windows/F73380/main.htmPlease let me know if this helps you.
Regards,
Jaya