In practice, I seem to wind up with the blue flame about 1/2" or so away
from the metal, depending on how much heat is in the metal, etc.

What I do is adjust the acetylene until its just barely stopped smoking.
This is the point where you get the "feathered" flame. Then I add the
oxy for a neutral flame.

It sounds to me that the OP needs a smaller tip anyway.

John