DynamicStreamItem: Passing Dynamic Streaming Paths

I am using the new Dynamic Streaming classes with AS3 and FMS 3.5.  I am storing four different streams in different locations on FMS.  Because I can only identify one URI, how can I pass the different paths for each of the F4Vs?

Example in brief:

...

private var _nc:NetConnection;
private var _ds:DynamicStream;
private var _vidDisp:Video;
private var _connClient:ConnectionClient;

private var _uri:String = "rtmp://myserver.com/vod";
private var streamName:String = "MyString";

...

var dsi:DynamicStreamItem = new DynamicStreamItem();
_ds = new DynamicStream( _nc );

_ds.client = _connClient;

_vidDisp.attachNetStream( _ds ); //Video

dsi.addStream( "mp4:" + streamName + "_150.f4v", 150 );

dsi.addStream( "mp4:" + streamName + "_300.f4v", 300);
dsi.addStream( "mp4:" + streamName + "_500.f4v", 500 );

dsi.addStream( "mp4:" + streamName + "_1500.f4v", 1500 );

_ds.startPlay( dsi );

What I would like to do is the following:

...

private var _nc:NetConnection;
private var _ds:DynamicStream;
private var _vidDisp:Video;
private var _connClient:ConnectionClient;

private var _uri:String = "rtmp://myserver.com/vod";
private var streamName:String = "MyString";

...

var dsi:DynamicStreamItem = new DynamicStreamItem();
_ds = new DynamicStream( _nc );

_ds.client = _connClient;

_vidDisp.attachNetStream( _ds ); //Video

dsi.addStream( "directory_150/mp4:" + streamName + ".f4v", 150 );

dsi.addStream( "directory_300/mp4:" + streamName + ".f4v", 300);
dsi.addStream( "directory_500/mp4:" + streamName + ".f4v", 500 );

dsi.addStream( "directory_1500/mp4:" + streamName + ".f4v", 1500 );

_ds.startPlay( dsi );

The only other way I can think of to accomplish this is to make the URI based on the QOS info but I'd rather not go down that road.  Any help would be appreciated!