Gentlemen,
Control line is growing again, probably a little faster than most realize. I know of at least 15 UC folks around here that were not here 5 years ago. They just do not join RC Clubs unless they do that too. As far as how much its growing, I don't know but I sell a lot more UC fuel now than I did 5 years ago and I see these new UC arf's at nearly every hobby shop now and the owners say that they sell but they don't fly off the shelf. These same retailers are now getting asked to stock a couple UC engines, UC fuel and some bellcranks and lines and handles , etc. Again, not setting the world on fire but its selling.
I myself just got back into it after not picking up a handle in over 20 years, my son digs it too, he's 11 and loves it mor than r/c.

Fuelman