How to render severals cameras at differents Frame Rate ?

Hi everybody !
I work on a project that require to target a good fps amount. In my scene I have two Cameras:
The main camera need to be rendered with a maximum fps whereas the second one is display on a renderTexture and can just be set to 30fps. I just want to know if it’s possible and if it can really increase the overall fps in the game.
I hope this is clear. Don’t hesitate to ask questions.
Thank you.

This might help

[RequireComponent(typeof(Camera))]

public float FPS = 5f;
public Camera renderCam;
// Use this for initialization
void Start () {
	InvokeRepeating ("Render", 0f, 1f / FPS);
}
void OnDestroy(){
	//CancelInvoke ();
}

void Render(){
	renderCam.enabled = true;

}
void OnPostRender(){
	renderCam.enabled = false;
}

Hello @Tiras69

The solution is to disable the camera component and use the Render() function at the rate you need.

This solution works, but for some reason it decreases the FPS for me, I am trying to find the reason at the moment.