The way I see it................

I strongly suspect your buddy's scale is off. I can't imagine a H9 Edge at 10.5 lbs!! I suggest you check the scale with a KNOWN weight.
Also, hooking to the tail wheel is not the most accurate method for measuring static thrust. There are several factors that will introduce drag which will lower your reading.

On my test bench I have my engine stand mounted on a ball bearing drawer slide. As the engine revs up it pulls the "drawer" forward. I have a nylon cord hooked to the rear of the drawer. The cord runs over a ball bearing pulley and drops 90 degrees toward the ground. I have a bucket hanging on the cord that I add weight to. With the engine at full power I load the bucket until it just starts to pull the drawer backward. I then weigh the bucket on a digital postal scale to determine how much static thrust the engine pulls. I insure that all this is LEVEL, and the thrust line is straight in line with the prop shaft.

Temperature, air density, and humidity will affect thrust as well. For a given prop and rpm reading - Cool, dry, dense air will produce more thrust than hot, wet, thin air.

The props...
Remember, the Composite APC 18x6W is a WIDE blade Fun Fly prop. The Wood Zinger Pro 20x6 is a standard blade prop. The Aerodynamic loading of the props is about equal. The APC weighs 4.4 ounces, the Zinger 2.6 ounces. The lighter wood prop presents less load at lower RPM, thus it will spin up quicker. Also, the Zinger is peaking at about 1000 rpm less than the APC, which puts it just below the peak torque rpm for the 160. Rate of acceleration falls very quickly once peak torque is exceeded.

Sorry to hear about your AW Edge. I still have my Edge, but have retired it. After all the repairs it just got toooo heavy and would not 3-D well at all.
This OS 160 is going into my new Lanier 120 size Edge.