I noticed that flexible phoenolic (ones that Red arrow and Giant Leap sells) aren't as waterproof as straight phenolic tubes. Especially the ends where the paper sandwich may be exposed. So next time you build something with those tubes please seal the ends with epoxy or CA. I know this from experience (I wet sanded one and I noticed that the ends were un-wrapping itself... had to fix it with a dab of CA)
Im just saying the flexible phenolics has drawbacks as well...
-- TAI FU