How to change button sizes depending on iOS device?

Hi everyone,

I am using code similar to the following to change button scale and position depending on whether the user has an iPhone or iPad... but it doesn't work. What am I doing wrong?!?!?!

  function Start () 
     {
         if (iPhoneGeneration.iPhone3GS ||
             iPhoneGeneration.iPhone4 ||
             iPhoneGeneration.iPhone4S (...and so on)
             )
         {
             // Pos x, pos y, height, width. Using screen height for both assures button doesn't deform
             GasButton.pixelInset = Rect (-64, -64, (Screen.height / 4), (Screen.height / 4));
             GasButton.transform.position.x = 0.93;
             GasButton.transform.position.y = 0.15;
             
             
         }
         else if (iPhoneGeneration.iPad1Gen ||
                 iPhoneGeneration.iPad2Gen ||
                 iPhoneGeneration.iPad3Gen ||
                 iPhoneGeneration.iPadUnknown)
         {
             // Pos x, pos y, height, width. Using screen height for both assures button doesn't deform
             GasButton.pixelInset = Rect (0, 0, (Screen.height / 8), (Screen.height / 8));
             GasButton.transform.position.x = 0.82;
             GasButton.transform.position.y = 0.4;
             
         }
     }

I should add, for the Android version of the game, the user can select whether they have a phone or a tablet, using the same code above, basically, and it works fine. It's the iPhoneGeneration enumeration that doesn't seem to be working for me...