Hello James Relyea,
In order to achieve your requirement, it is enough to set the SizeMode to Absolute:
.splitPanel1.SizeInfo.SizeMode = Telerik.WinControls.UI.Docking.SplitPanelSizeMode.Absolute;
You can review an example of such behavior in our Examples application, section SplitContainer >> FirstLook.
I hope this helps. If you have additional questions, feel free to contact me.
All the best,
the Telerik team