Just rely on common sense – quality JDM UL blanks have thin walls and low epoxy content. Don't step on them or hit them against anything – if they don't break right away they'll surely be bruised and may break down the road. Don't exceed stated lure weight, and you can cast without worries. Line rating has nothing to do with rod strength – lower limit tells you how well your rod can protect light lines and upper limit tells you how thick of a line the guides on your rod can handle.