Here's a picture of the DDM arm and deposition tip. My next step is to rebuild the arm portion. Notice that I am starting with the parts that are similar to what I've built before?
Same steps here, just delete the deposition tip and see what I can see:
This is the arm displayed in the tubes view. Right away I picked out six pieces, thinking that a single piece could be used as a moiety. This piece to be exact:
And if you extrude this, and manually bond the bottom carbons, you get the ring back:
Mine still looks a little loose because it has not had the energy minimized yet. But I'm on the right track.