The layout you have described is not anticipated for RadScheduler header, but you could achieve it with relative/absolute positioning of the arrows. For example as the following:
where x1 and x2 are your custom distances. I hope this was helpful for you.
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to the blog feed