One thing I certainly would not do is tighten a front wheel bearing past 0 clearance. Even with 15 years professional Mercedes experience my boss still will peek over my shoulder to make sure I do not overtighten a wheel bearing. There is a lot of range that could be considered loose that the bearing will work fine and last near forever. There is a very small range where tight becomes overtight which becomes a destroyed spindle. I always err on the side of a little loose. I consider this even more important on the newer cars with synthetic grease in the bearings. The syn grease doesn't flow when hot and tends to get pushed out of the path of the bearings. This essentially causes the bearing to run dry. Without a little clearance the bearings never see lube on the working surfaces.

I guess it depends on the application, but there is elastic deformity when loaded and you don't want excessive clearance when the bearing is loaded.

What does the FSM specify?

Actually I don't consider deformity an issue, thermal expansion yes. That said trying to get a wheel bearing in the tight end of the spec is only asking for an early failure. Remember that the "slack" in the bearing will be lateral, not radial. I could loosen your locknuts 1/2 a turn and you would NEVER know the difference from the driver's seat.

Thermal expansion is an issue, and as an Engineer I know that the outer race will also expand as it heats.

I'm not trying to re-engineer the thing, but I know that there are bearings that are designed to have play when adjusted cold and unloaded, others that are designed to have preload. I am just wondering which these are by the original Engineers' spec.

Fortunately, I have the FSM which specifies 0.01mm-0.02mm of axial play.

I'd imagine that 1/2 turn would give some pretty bad tire wear and stress the bearings un-necessarily.Whether I'd feel it in the driver's seat? I do my own alignments, I think I'd feel something that sloppy.

Adjusted per my instructions in a previous post should get you very close to the looser end of that spec.

The 1/2 turn, while hyperbole, I still maintain you'd never feel in the car. A good alignment rack could measure that but I know that I can't feel it while driving.

I'm not looking to start a flame war but I do want to emphasize this point to the DIY mechanic : a little too loose is fine, but even a tiny bit too tight can and will ruin parts fast

Not a flame war? Where's your rebel spirit?!

Agreed, a little loose in this case is better than too tight.