Tonight I dug out the center vent surrounds and internals. Putting these together isn't so much difficult as it is a sort of logic puzzle.
The internals are all pre-laser cut and fit together, some areas more snug than others. From my experience on the first R2, I decided to go with Super Glue this time around. It dries fast, clear and holds very well. I used the end of a small screwdriver to tap stubborn pieces into alignment.
I started with the top vent and glued the pieces together, first the base...and then the vent slabs, starting with the two that are the toughest to get at...the bottom and second one. I laid them in place then used the brush to apply Super Glue to the edge.
The lower vent internals required a lot of filing to fit inside the surround piece. Its slow work but with a Star Trek: The Next Generation marathon playing on the ScyFy channel, the time passed quickly!