I have been messing with a way to take your entire character, cut it up into multiple meshes so you can further subdivide each piece for more resolution, the problem has been that each piece now has different min/max displacement amounts so when you calculate all the different maps and render them you get seam at every edge of the seperate pieces.
So what I did was add a polygon to each piece that I will want to be a seperate piece and just place if off to the side.
So when you delete part of the mesh before you create your displacement map take you Intensity to 100 % and make a Z add adn Z sub tab on the poly that you have set aside, do this to all your pieces, if you go to the ortho view and just click the mouse once you will be able to reproduce the exact amount of displacement in positive and negative directions for all your pieces and now all you maps will calculate in the same grayscale range and you wont get seams inbetween them
here you can see the 2 different maps with the same color ranges, the trick to making this work is make sure that what you define as your min/max on the seperate poly is more than anything you sculpted on your mesh or it wont work, but this should be pretty easy to do, (you could always click twice to make the displacement more if you need) also be sure and leave a row of polys on the other side of your UV boarder or else you will get stretching at the edges, you can see the poly stip in the textures and the below image
Here you can see the low res mesh rendered with Mental Ray and there are no SEAMS!
Hope this helps and let me know if you need more info on any of this, its a really straight forward approach and should always work.