If I have learned anything from the various home video releases of Kubrick films and bizarre press releases regarding them, it's that Leon Vitali has a habit of contradicting himself and misremembering things. So I wouldn't put much weight into claims that Kubrick shot Full Metal Jacket for 1.66:1.
Everything between 1.33 and 2.20 is just personal preference. This is why I think certain terrible internet critics throwing around the word "bastardized" for transfers that dared to remove that tiny bit of extra masking for 1.78:1 transfers of films originally shown in 1.85:1 is total crock...