Flannel is tricky my suggestion is go touch and feel flannel some is light weight some is higher and better quality
Call and ask flannel is different than the cotton we use for our quilts. I don't remember if its the thread count per inch or how its weighted but I would do a little research first. the best flannel I have used is has been from my LQS
some is thin some is heavy I like the heavy. Lately I have been very disapointed with fabric.com and how they handle refunds when there out of fabric takes 10 days or so how ever I had great service from ericas when they sent the wrong fabric, they credited me right away told me to keep what they sent which was several yards of fabric.I did not want, I've donated it to charity. But I still had the option which is nice.