Vertical Forend Pistol Grip for Pump Shotgun

[BE Mike]

I've been contemplating a vertical pistol grip for the forend of a Remington 870. My concern is that of the rail of the gun holding up as it looks like it would be very easy to twist the pistol grip when firing. I haven't seen any good reviews of the long term effects of using one of these. I'd appreciate input from someone who has used something like the TacStar vertical forend pistol grip for a while.