Your picture shows one aspect of this that matching seams will not fix. Look at the width of the template lines on the rendered figure. Even though the body texture is ~1.8 times the size of the head - the lines on the body are much wider. The ears do not match the face and the back of the head does not match the front. If you had shown it, the hands and feet are the same - lines much crisper than the body. The neck to head you can play with, the rest are set. The wider lines also mean that the texture is spread out more. From the render, it is obvious that the difference is significant. The texture will be less dense the wider the black lines and this will make for a seam, no matter if your clone is identical. If your texture is rich, it may help if the clone on the body was much denser than the head. The nozzle/hose for the skin texture 100 pixels for the head, 25 for the body, back of the head, 50 pixels for the hands/feet, 75 pixels for the ears? the ratios are yet to be discovered. This would help a lot in the seam match where the resolution is different. This guide will be spot on for front to back ( except for the groin which is beyond hope). The thing there is to make sure you color outside the lines about half a facet more. You get white lines if you cut it too closely.