CORS in REST service when using Maps

I'm trying to setup a REST server with CORS support. I have created a class that handles a specific part of the service (printer control). This class I have referenced in my main REST class by adding <Map Prefix="/print" Forward="myClass.PrintAPI" />

My main class does have its own <Route>s and handles CORS requests perfectly. But in my subclass OnHandleCorsRequest() is only run when requesting from same origin and never run when making a CORS request. I have set Parameter HandleCorsRequest = "true" in both my main REST class and the subclass.

Can anyone point me in the right direction on what might be the problem or which alternative methods I should use and run?