Can I rotate my spacers after the stem bolts are tightened? No, not at all, on two different bikes.

I just barely tighten down the headset cap, straddle the bike, lock the front brakes, and rock the bike forward and back. It's easy to feel the "click" when the bearings are too loose.

My old bike needed almost no force on the Y wrench when tightening the cap. My newer bikes need a little more tightening force, but it's still easy pressure with two fingers.