I chucked my stepped reamer along time ago. Now I use nothing but a tapered reamer. First, you don't have to worry about having a SAE and a Metric on hand. Second, When the stepped reamer gets dull you cant' sharpen it without changing the diameter of the steps. With my tapered reamer I have sharpened it several times, and it doesn't change it's usefulness.

When I ream my props with the tapered reamer I go from front to back. I ream to the point to where the rear of the hub fits snug on the crankshaft. With the front of the hub ever so slightly larger than the rear it allows the back of the props hub to fit flat against the thrust washer but still keeps the prop centered on the crankshaft.

As Hobbsy says, A prop with a severely crooked hole is going to throw everything off. The crooked hole is trying to keep the hub crooked and the prop nut is trying to press the hub flat against the washer. This causes stresses on the prop, thrust washer, and prop blades which can cause bad tracking.

That's why I like to use my tapered reamer. It eliminates the fight between the crooked hole and the drive washer/crankshaft.

As for how far off I am with the tracking, it somewhat depends on how big the prop is. I have props from 11 to 18 inches. If I get them to 1/16 th I'm happy.