I am installing a VC Winterwarm large insert with flex connector and block off plate for a customer, he had the chimney cleaned and the chimney sweep told him to have it lined to the top. I believe the chimney is fine but the sweep does not want to deal with cleaning the connector next year. Anyway the customer wants it lined to the top. 12x12 clay liner 5 1/2 damper door. Looking for input I have done Winterwarm small with 6" flex pipe. This is the first time for a large with full liner for me.