We are seriously considering a 27RL. It seems odd the ones we have looked at have the Arctic Four Seasons Package but not the optional dual pane windows. The salesperson says they add a lot of weight, require more maintenance of seals due to weight, and make many sizes fixed instead of operable. He went on to say that their company and most RV manufacturers don't recommend dual pane windows. I emailed Grand Design from their website a week ago but never got a response. Can I get some input from others who have this option, or are familiar with the concerns raised by the salesperson. I want to get this right the first time rather than wish we had done something different after purchasing.