forward REST calls and retain path parameters

Hi, I have a controller which handles accounts, and forwards to the relevant controller based on the path, example below:

XData UrlMap
{
<Routes>

<Map Prefix="/:accountId/anothercontroller" Forward="AnotherController"/>

</Routes>
}

Problem is that inside AnotherController, the accountId path parameter is lost, I assume that's because the map forward simply checks if there's a match then forwards.

AnotherController:

XData UrlMap
{
<Routes>

<Route Url="/:somethingId" Method="POST" Call="CreateSomething"/>

</Routes>
}
ClassMethod CreateSomething(somethingId)
{
}

The reason for this is because I don't want to specify the same route including the accountId for many routes, instead is it possible to forward the accountId to get something like this:

XData UrlMap
{
<Routes>

<Route Url="/:somethingId" Method="POST" Call="CreateSomething"/>

</Routes
}
/// accountId passed through and accessible
ClassMethod CreateSomething(accountId, somethingId)
{
}

We'll be upgrading to IRIS soon, so if it is possible there I'd love to know where I can read more about how to do so.

Thank you.