The reason why the Checkers are bigger on the body and smaller on the head is because of the projection scale. When you UV maped the body, with whatever kind of projectiong, whether it be (planar, cyclinder, sphere, etc.) each projection should have a scale attribute input box, just go back into those projection and scale them to have all the same number.

so for example, if the body projection has 16 for the scale size, use the same number for the head projection scale attribute box number as well. and may be a good idea to keep it a square ratio, like 16x16 or 3x3. etc.

hope that helped, or if not i was probably thinking something else.