Textures Force-Scaled on Import. How to prevent?

So I'm attempting to scale a GUI that stretches across the bottom of the screen, but if I click the maximize on play the texture disappears. Upon further investigation, if I scale the width from the original size before maximizing it, it will disappear(EDIT: it appears now, but it doesn't stretch across the bottom, rather stays stuck at 1024x64). Here are the code snippets I'm using for this.

EDIT: I've discovered the problem. Upon importing the GUI image for mainImage, it resizes it to 1024x64. My screen resolution is 1366, and Unity won't draw the image more than its size. I unchecked the box that said "compress textures on import," yet it still resizes the picture to 1024x64. The size of the picture before this compression is 3298x205. I know, not a power of 2. I have re - saved it as 2048x128, and it still resizes it 1024x64. This is really frustrating :|. How do I go about overriding the compression? I tried the "override for compression for web player and stand alone", but that prevents code from changing it. I also added the manual image.height = scaledHeight and image.width = Screen.width. I get this error that says "Exception: not implemented" and not much more that I can see as relevant.

// main decoration textures:
var guiSkin: GUISkin;
var nativeVerticalResolution = 1200.0;
var mainImage: Texture2D;
private var mainImageOffset= Vector2(0, 0);

function OnGUI ()

    // Set up gui skin
    GUI.skin = guiSkin;
    DrawMainGUI (mainImageOffset);
    // Our GUI is laid out for a 1920 x 1200 pixel display (16:10 aspect). The next line makes sure it rescales nicely to other resolutions.
    GUI.matrix = Matrix4x4.TRS (Vector3(0, 0, 0), Quaternion.identity, Vector3 (Screen.height / nativeVerticalResolution, Screen.height / nativeVerticalResolution, 1)); 


function DrawMainGUI (pos : Vector2)
    var scaledHeight= mainImage.width / Screen.width * Screen.height;
    var scaledResolutionWidth = nativeVerticalResolution / Screen.height * Screen.width;
    GUI.Label (Rect (-pos.x , Screen.height  - mainImage.height-pos.y, mainImage.width, mainImage.height), mainImage);
    mainImageSize.width = Screen.width;
    mainImageSize.height = scaledHeight;

How do I stop the compression of my texture imports?

Edit: removed stuff irrelevant to the problem.

Use GUI.DrawTexture instead of GUI.Label

GUI.Label reads padding and stretching info from your current style, and applies them to your image, which means you'd have to create a style for displaying the image stretched properly

GUI.DrawTexture just draws a texture in the rect exactly as you specify