I've been using the Halibut version to good effect recently on a stretch where the Barbel have probably seen everything there is to see and are reputably very cagey. I tend to use a medium/large bread punch rather than cubes or ripping off chunks but I typically use more than one punched bit on the hair.
It stays on the hair very well, seems to resist the minor twitch/knock and has certainly worked recently. In the last few days I've had some fine Barbel including 2 over 11lbs and a new PB of 13lbs 03oz. The "13" came to a cocktail of Halibut and good old Sainsbury's finest Garlic Spam. All three of those doubles have come in bright sunshine and clear blue skies, which has been a bit of a revelation