My CF30QB has a very small toilet room. I'm not a big guy at 5' 11", but my knees were really close to the wall while sitting. Was able to remove the toilet, redo the plumbing & reinstall it about 2 3/4" further back. Doesn't sound like much, but it's made a big difference.
That's the one thing I don't like about our floorplan. I'm also 5'11 and find there's not enough room even to stand, but I get in, get'r done and get out. No reading the morning paper in there, that's for sure.