ok so you think it would be good with just one sensor on one cylender, all i need it for is for running in, to make sure it wont go too hot and lock up the piston
I would suggest that you research where they suggest to locate the sensor since I can't say, my equipment doesn't have any telemetry so I've never researched into it.
If you can accept a guess... I'd think you'd place it in a place central to both cylinders and not on just one or the other. This would allow you to monitor both and if the temps change substantially from the start of the flight, you'd know it's something to look into a potential issue to be resolved. Just remember that the temps will change with the environment so as the day's temps rise so will the engine's temps.
Going back to the initial testing it is not done with those sensors, it's done directly on the ground as you are setting up the engines fuel mixture etc, just like they do with real aircraft. The sensors are only for after the fact when the craft is in the air and then only as a reference not a diagnostics.