I must not be eating enough carrots. No way can I see an arrow flying close to 300 fps that's off 1/4" in flight.
But I get your point; you can tell a lot just by oberving the flight of the arrow.

Now, I will say that I believe paper tuning is a good starting point. Finish it up with a good session of walk-back tuning, as was described on here just a week or so ago, and then you'll be gettin' her dialed in.