Consider dropping the body texture altogether and replacing it with a simple 64x64 color chip for the skin. Group the tattoo area and assign it the texture "tattoo." Delete the group. Export the figure as an obj. sans groups and remap the tattoo area. Do your tattoo artwork on its own map (anything larger than the final resolution will work without fragmenting detail) and use the same bg color as used on the skin color chip. Reimport the model - which will conveniently come back in at the exactly the right place. You will save memory on the body tex, use only what you need for the tattoos, eliminate the use of memory for the "figure" instead of the re-imported model, and reduce seams caused by the renderer processing groups separately from each other. One can add any minor skin tex/grains easily in post. It doesn't solve your memory problem - but I find eliminating the body tex very helpful in most situations and it produces faster renders.