Question About MIdpointDisplacementHeightmap

I am attempting to use the MidpointDispalcementHeightmap in my game to generate its terrain at runtime. I want to do some manipulation on these height values in addition to the standard midpoint displacement algorithm, and, in order for this to work correctly, I need the output from JME values to be in the range [-1.0, 1.0]. I assumed that the range argument to the constructor would accomplish this, but, it does not seem to do so. Is there any better way of getting values in this range than resizing the values via a for loop, etc. after the midpoint displacement heightmap generates them?

    long start = System.currentTimeMillis();
        MidpointDisplacementHeightMap midpointDisplacementHeightMap = new MidpointDisplacementHeightMap(WORLD_SIDE_LENGTH, 1.0f, 0.5f, seed);
        heightmap = midpointDisplacementHeightMap.getHeightMap();
    }catch(Exception e){

    float v;
    for(int i=0;i<heightmap.length;++i){
        v = heightmap[i];

        System.out.println(v); //these values seem to be anywhere from positive 50-150

        /*custom manipultion here*/

        heightmap[i] = v;

    //create TerrainQuad, etc. from heightmap