Suspension can be a moving target sometimes.
As the rider's wants and needs from the bike changes over time. At 170lbs, I would say to stick with the stock oil weight unless there are some custom valves installed or future plans to race.
What are his preferred sag numbers and do you think they need to be changed?
If a 250 rider thinks the forks dive and the owner/rider agrees, then it sounds like the sag measures can go a bit tighter, ie add more preload. Different riders might shoot for different numbers even on identical bikes. What are the preload lines set at? For example, mine are at 3 for spirited paced street rides and track time.
So 2 clicks out on the low speed seems ok. How many turns out on the high speed (12mm nut)? There are no clicks on the high speed, just have to count turns. This is most likely what you need to adjust (assuming your preload is good).