I made my stooge from a flat plate of mild steel about 1/4 thick then bolted a similar pin with a spring as shown in the reply above. Instead of using nails to hold in place I use 4 rubber feet. The combination of steel plate that weighs approximately 10 lbs, with 4 rubber feet it does not move even with a 40 at full power. The trick is to have the plate heavy enough to hold the aircraft. The rubber feet are important to get a better grip to the solid ground.