My engine thrust testor is simple, accurate, CHEAP and can handle anything up to 5hp.

electronic 15# fish scale, 1/2" thick piece of EXT. plywood, a larger piece of 1/2" that is 6" X 36" long. Hole in the center for 2 flanged 1/4 " id bearings, backup washers, 1/4 " X 6" bolt and 4 nuts. 2 C clamps.

It has additional holes for different size engines and several scale holes at the other end to give ratios of other than 1 to 1.

It is bolted temporarly to the end of the table saw table. This allows me to wheel it out side for tests and it will not flip as the 2 C clamps limit travel to 2" max.

I always had the bad habit of OVER propping engines. By making the fuel tank free to be moved above or below the engine up to 10", I now know when I am over or under propped.

The Perry pumps are installed AFTER it can suck fuel great from 5" high to 5" low.

You are right if you see compromises in the prop sizes. I find it quicker to test on the saw than in a plane. AND the prop is ALWAYS way in front of me.