Hi Eric,
I think the most common pitfall on the Cigar pens is the bushing sizes,
or more specifically making sure you get the blanks turned to the right bushing at the right place so they match the fittings.
A common mistake is mixing up the upper and lower barrels,
the lower is a bit longer, and has smaller diameters.
If you turn the upper blank to the lower bushings, well..not good.
The lower barrel length is specific for the refill length to be right.
I usually mark each blank, upper and lower, then make sure I know what size
each end needs to be and match the bushings.
I mark mine A, B, C, D with a sharpie, and always turn from clip to nib as I go thru the letters.
You can even mark the letters on your blanks, after you are sure, but that might be a little overkill!
Enjoy your first Cigar!:biggrin: