Easier Sag Measurement
I apologize if this is a repeat.
I use a nylon tie strap as a "tattletale" when setting shock preloads using the following procedure.
Fasten a tie strap around the shock absorber rod and trim the end well within the spring. Raise the bike to full shock extension and push the tie strap tight against the shock body. Lower the bike and apply whatever load you are preloading for.
Raise the bike to full extension again and measure distance between the tie strap and the shock body to obtain the sag measurement.
This method is easily repeatable and can be performed by one person. Additionally, the "tattletale" can be used to measure maximum suspension travel under actual road conditions as long as the shock is not bottomed during the test.
Again, sorry if this is a repeat.