Procedural Island Terrain Generation

Edit: Rewrote my question after trying a few things and made it more specific.

Hi, so I'm creating a mobile RTS game with procedurally generated maps. I've worked out how to create a terrain with a basic perlin noise on it, and tried to integrate http://gamedev.stackexchange.com/questions/54276/a-simple-method-to-create-island-map-mask method to creating an island procedurally. This is the result so far:

As you can see, the edges are great but the main area of the island is completely maxed at 1 and completely un-random in shape.

The image below from http://www-cs-students.stanford.edu/~amitp/game-programming/polygon-map-generation/ shows the kind of terrain I'm after. The tutorial there is great but would be too intensive, thus the post.

I want the Random Shaped island with Perlin noise generated land mass, surrounded by water.

edit: I've narrowed the problem down to the somewhere in the last 3 functions and I don't quite understand it enough to figure it out.

Here is my code. A script attached to a null with a button to activate Begin():

 using UnityEngine;
 using System.Collections;
 using System.Runtime.InteropServices;
 
 public class Gen_Perlin : MonoBehaviour {
 
     public float Tiling = 3.0f;
     public float min = 100000.0f;
     public float max = -100000.0f;
     private bool active = false;
     public int mapHeight = 50;
     
     public void Begin()
     {
         if (active == false) {
             TerrainData terrainData = new TerrainData ();
             const int size = 513;
             terrainData.heightmapResolution = size;
             terrainData.size = new Vector3 (2000, mapHeight, 2000);
         
             terrainData.heightmapResolution = 513;
             terrainData.baseMapResolution = 1024;
             terrainData.SetDetailResolution (1024, 1024);
 
             Terrain.CreateTerrainGameObject (terrainData);
             GameObject obj = GameObject.Find ("Terrain");
             obj.transform.parent = this.transform;
 
             if (obj.GetComponent<Terrain> ()) {
                 Debug.Log ("Gen_Begin- " + obj);
                 GenerateHeights (obj.GetComponent<Terrain> (), Tiling);
             }
         } else {
             GameObject obj = GameObject.Find ("Terrain");
             if (obj.GetComponent<Terrain> ()) {
                 Debug.Log ("Gen_Begin- " + obj);
                 GenerateHeights (obj.GetComponent<Terrain> (), Tiling);
             }
         }
     }
     
     public void GenerateHeights(Terrain terrain, float tileSize)
     {
         Debug.Log ("Start_Height_Gen");
         float[,] heights = new float[terrain.terrainData.heightmapWidth, terrain.terrainData.heightmapHeight];
         
         for (int i = 0; i < terrain.terrainData.heightmapWidth; i++)
         {
             for (int k = 0; k < terrain.terrainData.heightmapHeight; k++)
             {
                 heights[i, k] = Mathf.PerlinNoise(((float)i / (float)terrain.terrainData.heightmapWidth) * tileSize, ((float)k / (float)terrain.terrainData.heightmapHeight) * tileSize);
                 if (heights[i, k] > max) max = heights[i, k];
                 if (heights[i, k] < min) min = heights[i, k];
                 heights[i, k] = makeMask( terrain.terrainData.heightmapWidth, terrain.terrainData.heightmapHeight, i, k, heights[i, k] );
             }
         }
 
         Debug.Log ("Set_Height");
         terrain.terrainData.SetHeights(0, 0, heights);
         Debug.Log ("Done");
         //this.gameObject.AddComponent <Gen_Prefabs>();
     }
 
     public static float makeMask( int width, int height, int posX, int posY, float oldValue ) {
         int minVal = ( ( ( height + width ) / 2 ) / 100 * 2 );
         int maxVal = ( ( ( height + width ) / 2 ) / 100 * 20 );
         if( getDistanceToEdge( posX, posY, width, height ) <= minVal ) {
             return 0;
         } else if( getDistanceToEdge( posX, posY, width, height ) >= maxVal ) {
             return 1;
         } else {
             float factor = getFactor( getDistanceToEdge( posX, posY, width, height ), minVal, maxVal );
             return ( oldValue + oldValue ) * factor;
         }
     }
     
     private static float getFactor( int val, int min, int max ) {
         int full = max - min;
         int part = val - min;
         float factor = (float)part / (float)full;
         return factor;
     }
     
     public static int getDistanceToEdge( int x, int y, int width, int height ) {
         int[] distances = new int[]{ y, x, ( width - x ), ( height - y ) };
         int min = distances[ 0 ];
         foreach( var val in distances ) {
             if( val < min ) {
                 min = val;
             }
         }
         return min;
     }
 }