Oil weights effect damping very different than preload.
the objective starting g point for preload and spring weight selection is achieve about 20% static sag with the bike fully loaded
it takes 3 people to set up suspension sag
the rider in full gear
one person to balance and steady the bike with the rider on in riding position
one person to take and record suspension compression measurements
when corrected for stiction, a bike with 5" of total travel should be set to 1" of sag fully loaded
im me if interested in the full procedure