for the lil Cox engine - --I still have TeeDee 10/20/49-- and for small electrics -here is the thrust stand I designed -which I also use to prove real thrust and power consumption-not calculations-
The little wheeled carts etc-- are simply to much work -for me and this has ONE moving part.

The principle is obvious - a 90 degree arm with pivot at base.
the oz/grm digital scale reads accuratelyand they are available anywhere at office supply outlets.
stand material costs - buck or so