I used barbs I got from Dangerden because I found they have slightly larger ID than other barbs I have around the house. They aren't a perfect fit; some torque required. 1/4" NPT x 1/2" barb. I think the thread is actually 1/4" BSP. FYI, 1/4"NPT x 3/8" barbs will thread in perfectly with no force. I am guessing that there is something related to the taper of the threads at play.
I will likely add a UV CCFL at some point just to verify no leaks ever crop up