Prefab instantiated off screen problem

Hi everyone. I am working on a 2D shooter game, kind of a spin-off of Space Invaders. The "enemies" are generated on the left/right side of the screen (side being chosen at random). The ones generated on the right are slightly higher than the ones on the left so that they do not collide.

I have a small problem. On smaller screens, all enemies are generated as intended. However; on larger screens, the enemies coming from the right (top) are being generated above the top of the screen therefore never seen by the player. Here's the code I am using.

 function GenerateEnemies()
 {
     var tempEnemy:Rigidbody;
     var enemyDirection = Random.Range(1,3);
     var posY1 = topMargin-30;
     var posY2 = topMargin-60;
     
     if(enemyDirection == 1)
     {
         tempEnemy = Instantiate(enemy,Vector3(rightMargin,posY1,8),Quaternion.identity);
         tempEnemy.GetComponent(EnemyBehaviour).direction = 1;
     }
     
     if(enemyDirection == 2)
     {
         tempEnemy = Instantiate(enemy,Vector3(leftMargin,posY2,8),Quaternion.identity);
         tempEnemy.GetComponent(EnemyBehaviour).direction = 2;
         tempEnemy.renderer.material = enemyMaterial;
     }
 }

Thanks for any help.

Matthew