I have done a king size with a 9 x 5" throat machine and didn't have to turn it. Pay extra attention when rolling it up on the takeup roller to scrunch it up tight and I used Hobb's 80/20 batting. Puffy batting might not work so well but as PaperPrincess said, you can turn it which is what many folks have to do with a 9" machine anyway.
I don't have any trouble with fleece because it is super squishable. I have more trouble with poly battings. The foot gets stuck on them so I have to cover the edges with tissue paper and quilt through it.