Ray-
I first want to admit that I am not a machinist. I originally was going to tap my banjos with the 1/8" NPT tap. However, after careful measurements with my calipers, I just did not feel that there would be enough meat left to the bolt. Have you really found differently? I'm tapping with 1/16" NPT instead, and then flaring to 1/8" NPT female with the Autometer 3280 adapter.
UPDATE:
Excellent solution! Ray just informed me that he is making his own banjo bolts from 3/4" stock rather than using the existing as I have done.