I've now run into a couple of minor issues that would have been much easier to rectify earlier in the build than now.
First is the balsa plug that is essentially the shoulder of the nose cone. It fit beautifully into the opening in ring #7 which is the nose cone base. Unfortunately, it's too fat to fit the BT50! I didn't check this prior to gluing it to ring #7 and then adding the cone shroud. Sanding it to size now is just a bit trickier than it would have been.
Secondly, the BT50 is slightly too long. I actually made a mental note that it was about a 1/4" or more longer than the specified dimension in the instructions, but I was hesitant to trim it then, not sure where it would end up when fully assembled. You can see in this photo the difference in how much gap there is between the nose cone shoulder and the top of the BT50, and the remaining gap between the nose cone itself and the BT70.
Again, not difficult to fix, but it would have been easier to do before being assembled.