I keep a core in the basket. It seems to keep the vinyl from tenting up in the middle. I do a run of a roll of arlon slx every few months with 10' plotted sections, and for whatever reason it has a really bad habit of trying to fold over the front edge of the basket, so you have to gently nudge it backwards so it folds backwards instead of forwards (over the basket edge). I finally figure out I could just put a core, suspended on a piece of angle, right on top of the basket rails, about 6" from the front edge, so when the vinyl starts to stand up it bumps the core and folds backwards.
If I had a fc9000, I'd buy that dang takeup reel!