The nacelles are finished!  I've been hesitant to actually assemble them because I had essentially two chances to get it right before something got damaged.  There were so many potential problems with this step, I was seriously stressing over them:

• The paper over the blue LEDs could tear
• The paper over the bussard collectors could be too thick for the fore section to fit properly
• The warp plastic may not fit properly (there's no way to align it when the halves are together, I can't reach the plastic through the blue LEDs and the onion skin paper!)
• The blue LED post could snap / bend in contact with the upper port / starboard indicator
• The upper port / starboard indicator could break against the blue LED post
• The play-dough could shrink and come loose over time, causing the nacelles to rattle and the lights to leak severely.

     Turns out that after all the stressing, when I sat down and did it they went together perfectly.  In their final assembly, I performed the following steps:

• Applied onion-skin paper over the bussard lights so as to smooth out the light (looks better)
• Glued the warp plastic to the bottom half as carefully as I knew how
• Formed the play-dough between the bussard and warp sections, applied glue to top and bottom
• Slowly put the aft section together, held it with a rubber band
• Twisted the upper half in place (so as to fit over the blue LEDs and not tear the paper)
• Pushed the two halves gently together, compressing the play-dough and aligning the warp plastic
• Put a rubber band over the fore section
• Glued the shell
• Glued the upper half of the warp plastic

     The result is a damn fine looking pair of nacelles, if I do say so myself.  They weren't perfect as soon as the glue dried - over time the play-dough did shrink a bit (but it shouldn't rattle as it's stuck to the LED and wires).  I squirted some caulk in there and used a toothpick to decrease the light leakage.

     Needless to say, I'm breathing a little more easily now.  This was a very rough step.