1)Chuck Norris=92s left and right fist are deadly weapons
2) Chuck Norris=92s left and right fists are deadly weapons
It seems to me that 1)=97with fist singular=97is grammatically correct because the conjoined adjectives expand out to =91left fist and right fist=92, which is the required meaning. Why then does 2) =97 with fists plural=97 =93sound=94 better? After all, it expands to the incorrect =91lef= t
fists and right fists=92, implying a four-handed Mr Norris!

cf Mr Smith is Chuck Norris=92s and my friend
Chuck Norris=92s and my friend know each other.
Thanks
Simon G
Melbourne, Australia
(Email Removed):
1)Chuck Norris’s left and right fist are deadly weapons 2) Chuck Norris’s left and right fists are deadly weapons It ... Smith is Chuck Norris’s and my friend Chuck Norris’s and my friend know each other. Thanks Simon G Melbourne, Australia

Your ears are right: sentence 1 isn't grammatically correct, and if it were his feet rather than his fists, we'd get ' left and right foot are deadly weapons', which sounds even worse.
I don't think your expanding (out) is a useful exercise. 'A railway between the French and English capitals' doesn't imply 'French capitals and English capitals' at all.
Since we only have two fists your sentence is a bit odd anyway. Why not say his fists are deadly weapons, or each fist is a deadly weapon, or both of his fists are deadly weapons?
Your comparison sentences don't seem helpful here. They're fine, as you know, though I reckon the use of 'mine' helps.
Mr Smith is Chuck Norris’s and my friend.
- Mr Smith is Chuck Norris’s friend and mine.
Chuck Norris’s and my friend know each other.
- Chuck Norris’s friend and mine know each other.
Peter (UK)