That is a very interesting suggestions Frank! I will see what I can do about that. Thanks for the guidelines for the blur radius Oshyan, I wasn't noticing much of a difference between the default 8 and 24, 32 etc. Sometimes with the sliders you really have no idea what sort of range you should be going to.
I have made quite a few major changes so far, some based upon studying Martin's canyon wall file, and others for the sake of render times. Here is a higher res image (currently frame 77) The walls have been reworked, and unfortunately for now anyway the water is gone. At 0.5 detail, 16AA, 3/3 GI at 720x400 this one took 28 minutes to render, so I am close but not quite where I would like to be for the full animation.