My 2007 Iron barrel has a little nub, but beware: that nub is the base of a threaded cylinder stud, not where the breather went. The breather would have been below it.
Frankly I can't see how that will work with the cylinder in place the liner will block any cylinder pressure getting to the fitting you've put in there. I think you'll have to mill a passage to the crankcase area below to get it to work. Don't have a bullet apart to check this but all the twins I have are cut like what I described above. Maybe Ace can fill me in on this. ERC