texture stencil

Hi every time i try to paint a model using texture stencel blender freezes on me ,
The head model is low poly 2 sd , normals outside no double verts ,2048 uv map.
i have photos of the model iv made but blender crashes a little way in to the paint prosses.
pc , i7 3773k .32 gig ram nvidea gtx760 2gig. blender latest version .
Any help on this , i dont upload file date sorry .