Monk AC & Weight

[Nerrp]

Is there some "behind the scenes" magic happening with AC and weight? Or is the "weight penalty" as simple as exactly what it shows you as your new AC?

Specifically, if you equip a heavy item with AC, but the NET Armor Class shown is positive - is it "worth" putting on the extra armor class from the item?

Is armor class "what you see is what you get" on the stats in terms of weight penalty?