I used to use Q-tip tubes - there is one major reason why I no longer do - they are very fragile. I have had them break from getting too cold and brittle, from banging them on rocks as well as hitting the forward stroke a little early. It really pissed me off to have a pefectly good fly break in the middle! On top of that I also had issues with getting the finished fly off the mandril - the thread pressure would squeeze the tube down
As I've said in other threads - I now use air brake tubing for most of my flies and narrow graphite tubes from rod tips for my low-water type tubes. My advice is to stay away from Q-tips (then again, if you want I have a couple of large bags of them somewhere that I will never use - except to clean my ears!).