I found the ones on the Cent Omni to be far superior to those on the Ghost. The Ghost ones, for whatever reason, gave me way more trouble. I've probably done four or five Cent Omni's now, and I've done the shoulder nubs on every one.
I put the nubs on a Blade I built recently as well, and those were slightly easier. The nice thing about the Blade nubs was that, the way they were cast, I could leave them attached to the sprue and use the sprue as a really long guide to hold on to while installing the nubs. They were still light enough that they super glue would hold up the whole piece and I could trim the sprue off once they dried. If I recall correctly, the nubs on the Cent Omni are cast such that you have to cut them off the sprue before you can glue them on. They are upside down compared to the Blade. However, the exposed tops of the nub ended up cleaner on the Cent Omni, so really it's a trade off.