you don't need to go forking out for a q-lok, if you can get/afford it then thats great, if not a normal twistlock neck is fine, (and alot cheaper lol) i may have one lying around, if i have, i'll bring it to quadball on mon night, i know this fits a halo as i used it at the masters with an ion and feed neck.
Also as neil said try taking out an o-ring from the stock feed neck, this helps too.
Also as neil said try taking out an o-ring from the stock feed neck, this helps too.