Years ago I cobbled up a jig using an electronic fish scale. Wooden fixture clamped in a bench vice. Scale mounted to fixture with a rod mounted to the hook. Pass the spring through the rod, and attach a nut then pull down the spring with a block mounted above the spring. I attached a witness line on the the fixture next to the spring as a reference for compression. Compressed the springs to about 90%. Seemed to function just fine.
