Originally Posted by
Slpmama123
This is kind of what I was thinking, I was leaning towards flannel partially because I thought I could get away with less quilting if I used it
My 3 or 4 inches answer is a conservative guess based on what flannel seems most similar to. I don't actually know and haven't used flannel as batting before. A flannel sheet probably doesn't bunch up as much as batting does, so it may be possible to quilt it farther apart. Hopefully someone who actually knows will weigh in.
If you want batting that needs less quilting look for polyester or cotton with a (polyester) scrim (and as someone said, read what it says on the packaging about how far apart it can be quilted).