Good question.
I use a plastic supermarket bag. the bag handles hang great on my scale's hook. I tried hooking through the lower lip, but they flip when you let go of their jaw. It also seems like it causes a lot of damage. I figured that the bag is better for them than flopping around on my deck. I hope this isn't harming them too much. If it is, will somebody let me know? I only wheigh the big ones (well big for me anyhow).

I have the Berkely digital to 15lbs. I checked it on a dogfood bag at 10 pounds and a catfood bag at 3 pounds. Both read slightly over, so I think it is pretty accurate when you account for the wheight of the empty bag.
NoTrollMotor

NoTrollMotor