hi, sorry for taking a focus of this thread a little aside. But it's very related question. In a few days I gonna install BB to my new frame. After chasing n'facing (it was a brand new frame) I got BB tube shorter (rated 68mm). Now it is 67 mil. I have integrated BB with external bearing cups. I see two options: use spacers or throw away the shell connecting left and right cups. Some models I know have flexible plastic shells, but mine is made of ceramic and will not compress. I now pass by the question about chainline. Offcourse I'll use spacers if I'd need to correct it. But what if all turn out beautiful, is that plastic part is great of importance?