The guys in the Tach Readings forum on RCU report peak rpms of 10,500 to 12,000 for their G90's for 13x6 props. This gives static thrust 8 to 9 lbs for most props.
I used the the reported rpms and a thrust vs rpm map I have developed for a variety of props. I plotted thrust vs rpm using software " Prop Select " and plotted as much measured data as I could find on the map to verify or correct the curves. I have found Prop Select predicts thrust well enough for me. I agree thrust is easy to measure. Much of the data on my maps was measured by me using a fish scale that I calibrated with known dead weights. Most people don't need to know thrust to a very high degree of accuracy as they use it to predict how an engine/prop/plane combination is going to perform which can only be done approximately.