I agree about the flannel. If the new flannel is very soft and thin, avoid it like the plague! However, if you can find heavier flannel, grab it!
When I make things for dogs (think scratching and dragging), I use 1/2" seams and make my stitches a bit smaller. I also make sure the fabric is sturdier cotton (not stiff, just heavier). My point is, if it can stand up to dogs "digging" at it, it can stand up to just about anything.