Really?Thanks for the link - been meaning to search for butyl tape. It seems it's widely used in the USA but haven't previously seen it around in Old Blighty.
1) Does the team think 3mm thick is enough (before compression by the fitting)?
2) Anyone any experience of 'Bear Tape'? I've seen it on sale in a couple of places with no explanation of what it is. This ad (probably not the cheapest it can be found) says it's 'vinyl foam tape' http://www.mailspeedmarine.com/marine-tapes/psp/vinyl-foam-tape2724-272991.bhtml .
Really?
I have been using it for at least ten years.