Hello Andy Smith,
The SiteMenu has a property called StartingNodeUrl which you can use to select the starting node from where the RadMenu binding will start. You can add the code below to the SitePanelBar or your custom control to expose the same functionality for the RadPanel bar control
.SiteMapDataSource1.StartingNodeUrl = value;
Another option is creating a custom controls and bind them to the pages you want.
You may find this post useful - SiteMenu Builder
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items.