I made a wooden test stand with an upright (90 deg) screwed and glued together with 45 deg bracing (bullet-proof!). Then I use a cheap Great Planes engine mount drilled and tapped for the particular engine bolted to the upright with "T" nuts. Fuel tank is held on the back of the uprght with rubber bands into screw in coffey cup hooks (tank wrapped in foam). When I break in a new engine, I just use the mount for the intended plane or buy another cheap GP unit just for the break-in. I bolt the entire thing onto a saw horse with two 1/4" lag bolts, and also put a 25# weight on the bottom of the saw horse to keep it from "walking" at full throttle run ups.