I'm getting conflicting advice and I dunno what to do.

I spoke to warranty at the Hinckley factory today and the bloke I spoke to (Mark, I've spoken to him before and he seems sound) advised against changing jets and just use the adjusters on the carbs to correct the mixture. He said that, with the mods that I've done, there should be no need to change anything internally.
Thoughts?
PS I've still not checked the plugs: am I right in thinking that it's a 18mm plug socket? Seems hyooge!!