After setting your attack/release times try playing with the curve in the graph (this will make it even more natural and coherent in some situations). Just use 1/2 as your Source Audio Channel, not so fast attack and long release times (maybe you'll need to tweak a bit the Input minimum value to make it work properly). You can easily shape your tracks dynamics with JS volume_pan and get pretty good results (I do it on every mix).

Wouldn't it be possible - using Parameter Modulation with perhaps some additional (rea-)effect - to more or less 'imitate' Waves Vocal Rider? Therefore I'd like to ask what you deep core Reaper experts think: Now, I'm not the greatest expert in the Parameter Modulation-area, but I've experimented a little and found that a simple 'gain rider' is a piece of cake to accomplish. When I first read about it (at Waves and on Gearslutz ()) I instantly thought of Reapers Parameter Modulation.

As you probably all know, WAVES recently announced their new plug-in Vocal Rider () (here's a Video () from AES 2009).

Vocal rider plugin free