Does anyone know what the operating limits of a 50 Hyper are? what is average, high, too high?

Depends on where you are taking the temp. Most of us stick our fingers on the back plate immediately after we land (well wait for the blades to stop spinning) and if its too hot to hold your finger to it its too hot, if you can hold it there for a bit but its warm thats perfect, if its cold you can go leaner for more power.