Thanks for the suggestions on the website via the link. Having given it some thought, and just finding a large redundant cylinder cover as source of material, I think I will remove the existing flange completely and fit a larger one. I shall loctite it onto the turned down cylinder end, then drill and tap small holes on the joint line, and inset plugs of threaded rod, again with loctite, to form a mechanical join as well as glue. Probably not needed, but I am a belt and braces man. Thanks again
Maurice Cox