[DS4.5] Need help with UberSurface2 - second layer vastly increasing render times

Hi there,

I'm working on a picture of a werewolf character I have, based on the M4 Dog World: Wolf ported to Genesis. Anyway, I decided to use the second layer of UberSurface2 to add detail to the texture, using some stock images of wolf fur, but it turned what was about a 2 hour render into an 18 hour monstrosity.

Obviously this isn't practical, and I'm hoping someone here will be familiar enough with the shader to explain what aspect is most likely to be causing the huge increase in render time. It's worth noting that using the US2 Layer2 presets, even on many surfaces, increases render times by, at most, 33% -- so clearly something is not optimal in the custom settings I've used.

On all the body except the nails and face (so pretty much every surface preceded with a 2 or 3) I have used textures for Bump2 and Diffuse2, with the Blend mode set to Multiply, strength at 65% and Blend Mask Blur at 1% -- it's this last setting that I suspect may be the issue, or possibly because the diffuse textures are of quite large dimensions. I am unsure if removing the bump map would make a significant difference; I'm simply not familiar enough with the shader to work out what's making it take such a long time and trial and error on every setting would be far too time consuming.

I've looked at the documentation on Omnifreaker's site and it's really not clear what aspect is causing the render times to be so much longer. The result has come out well but I cannot have my computer be entirely occupied with rendering for 18 hours each time, so I really need to figure out some way to speed the process up as I will no doubt need to make a few more revisions before the picture is finished.