The exploding box problem is (if I understand it correctly) due to the way Poser likes its displacement maps. Other 3D software usually takes 50% gray as the midpoint - i.e. no displacement - with black indenting and white extruding. Poser, on the other hand, takes black as the no displacement point and any lighter colour will therefore extrude - so, the exploding box. To get round this, plug your displacement map into the value_1 input of a math_function node set to subtract, with value_2 set to 0.5. (This assumes the background of your map is 50% gray - you may need to tweak this value slightly.) This will subtract 0.5 from each value input from the map, and means that black now has a negative value and will indent, and white will still extrude (although it has a lower value).

Steve