The last test on the propeller parts, except for balancing, was the spring load test.
There is two compressed states that needs to be read, at 125,22 mm and at 90,93 mm.

I welded a tube cut to 90,9 mm to a steel plate, to keep the spring from jumping out during compression.
Then I used a calibrated aircraft scale, to measure how much weight it took to compress the spring, first to 125,2 mm:

The required weight was 74 kg, which equals 725,69 N. That is well within the range of 649 to 796 N.

Then I compressed the spring to 90,9 mm. The scale read 148 kg, which equals 1451,38 N.
The range at this height is 1254 to 1535 N, so also ok.