I'm constantly striving to be less uncomfortable in the saddle. I think I have my fit nailed down, except for my saddle setback.

Generally, if my saddle is level, and I let go of the bars while pedaling, I tend to slip forward on the saddle a tiny bit. When I move forward on the saddle towards the nose, and do the same test, I don't move at all. My setback is about 7cm, and I am slightly behind KOPS, for reference.

From this info, does it seem like I need to move my saddle forward a hair?

Yeah, give it a try.

As I remember, when your set back is right for you you can move your hands from the tops to the drops and vice versa with out hurry, no problem.

KOPS/"balance when hands are off the bars" will get you close, but once you are close, your body will put your butt in the "best" position based on your other two contact points and saddle height. Then, use small saddle adjustments fore/aft to make that "best" butt position as comfy as possible.

In other words, if I slide my saddle 1.5 cm forward from its current (proper) position, it is not going to make me move my butt 1.5 cm forward when I ride. My butt knows where it wants to be, and the small saddle tweaks fore/aft are just to make that spot as comfy as possible.

You gotta go where your butt wants to be! I'll give the slight forward move of the saddle a try tomorrow morning!