Turning a 12 foot long part.... how?

Using a 4 independent jaw chuck. A steady rest and this thing called a follow rest that I've never used before that just rides the part with brass tipped ends.

I keep getting chatter in the middle of the part. And it's too long to use a tailstock or else I end up with Un cut material in the middle after I flip the part around in the lathe.

Longest thing I've ever cut, tolerances aren't tight but it keeps going wrong and super chattery.