In my haste, I bolted in the wrong bolts. They were the right size but too short as the thread wasn't through the nylock part of the nut (possible IVA Fail) and I then noticed the shank wasn't deep enough on longer ones that I bought, so changed them for longer shanked ones.Then for some reason I realised I better keep them the same length for balance purposes seeing as the prop shaft is balanced too.
So I took one out that was shorter than the rest.
Glad I spotted it now before the body goes on.
Maybe a bit too picky, but I don't want to risk driving about wandering what that shudder is.