Andrew,

Looking good........

I have run pull/pull rudder set-ups with and without the plastic tubes. I have even run them with just a short piece of tubing at the exit. I make my decision on the plastic tube based on how difficult it will be to run the "cables" through the finished fuse. I also consider if there is a chance for the cable to be rubbing on a bulkhead or something. If that chance exist then I use the plastic tubing.

My preference is certainly to pre fit everything at the stage you are. In other words cut the exit slots if I am not using tubing or run the tubing now if it is to be used. I would pre fit the control horns on the rudder and do a mock up with rudder and vertical stabilizer in place to mark cable exits. Typically I will not fit the cable (cut it to length) until after all assembly and covering is finished.