Yes, that's the reason why I use it. When testing our very powerfull engine that has a very low fuel consumption even at rich run. I got bored at flying 13 minutes with 4 sec. laptime when something went wrong. It saves the engine and airframe.
Actually, even when FAI rules allow its use (don't know about AMA), I don't find it so important in competitions. For sure I will use it but I've never really had issues with engine stopping too late (knock-knock..). I will still continue to fill the tank for 6.5 minutes flight, just in case.
There are other benefits than just avoiding overtime, like a possibility to choose the point where the engine stops, it is very usefull in strong wind. Often the engine likes to stop when model flies against the wind and that is not good for landing glide. Also, as the engine does not get the last bubbly fuel in the tank, it will not go lean in the end and stops more quickly. That's also good for landing glide speed.
My clamp is mounted be in the 10mm wide space right between needle valve and tank front end. You can see the mounting holes in the tank mount. I think thats an ideal situation but I don't know what the effect will be when the clamp is further back from the carburetor.
With front intake engine, the device can be bolted in to backplate or mounting lug for example. Receiver, servo and battery are just in front of bellcrank.