Thanks for the replies to my questions, everybody.

Yes, I suppose there could be liability issues with a Knight with a missing vent liner that is sold second-hand. In this sue-happy world we live in anything is possible. I never thought of that one. I wonder if Savage has ever had an issue with that.

Also, I did not realize the vent liners were that hard and durable. Guess it's not an issue, huh?