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And yes, bigger dimensions means slower render - if you think about it if you double the dimensions you square the area so I'm guessing the render time would ramp up accordingly. What also has an effect is 'the geometry'. If you can cut down on stuff in the scene then the render engine will have less to worry about (the Reality plug-in has 'poses' to hide various body parts, including tongue, teeth, etc.). High levels of gloss will also drag out render times, and as Reality takes it's initial glossy setting from the DAZ material glossiness that can often be far too high. It's quicker and easier to do bulk glossiness setting changes in DAZ. Closing Reality and going back to DAZ to adjust stuff like is not an issue (so long as you have yet to set off the actual render) as Reality will remember any tweaks you have made thus far.