I managed to do some more blender work today. here is the 2 cliff sections with their unique normal (low frequency) layers. they share the same diffuse, spec and normal detail (high frequency) layers.
although not very obvious from this camera distance and fov, I couldn't find a way to tile the materials across the sections so there is a seam. this was due to apparently the baking needing all the uv's to be within the default image space, usually uv's can extend beyond that space if the materials use tiling diffuse, spec layers etc.
@ kat, did you find the same limitations with your tiling prefab rock models?