One thing that people seem to keep overlooking is that the overall weight of the trailer is not (directly) connected to the amount of squat/sag. You could have a 10,000 lb trailer connected, but only have a 200lb tongue weight (granted, you'd be subject to a lot of sway with that setup, which is why I said it's not "directly" connected, because your tongue weight should be at around 10-15% of the trailer weight) so your 10,000 lb trailer would cause very little squat/sag. However, on the opposite end of the spectrum you could instead end up with a 5000 lb trailer with 1000 lb of tongue weight, which would cause a lot of squat/sag.
When you post information about how much your truck sags, it would be really nice if you could post the tongue weight also if possible, rather than just the trailer weight and/or truck weight.