Yes larger bucket = faster render, until you start swapping which depends on the complexity of the scene and your system. Simple scenes (1 figure and some hair) I can set it to 64 or even 128. Complex stuff, like a world scene, 16 or 32 yielded faster results. I assume this was due to disk thrashing. The Stock draft render shading rate is 2, Production rate is .5 Smaller numbers = slower render. At least that's the way it works on my SP1B. For example: Ball Prop on the ground 2.0 Shading rate renders in about 7 sec. Same scene with .1 Shading rate was 42 Sec. Yes, back facing polys have little or no effect on render speed, but if fire fly decides to cull the wrong polygon (which it has done to me) you have to re-render with that setting turned off. Actually I don't think it's done it since the patch maybe I'll get brave and leave it on to see if that bug is fixed. I hadn't tried turning the smoothing off on body parts. I takes so long to get a render I kind of inhibits experimenting with settings. The only difference is that I used the Full Patch. Would you double check that shading rate thing. If the settings are really different for different patches they need to straighten that out.
See I told you milage would vary ;-)