If the train was full in peak season, even if no tour passengers were aboard, you would have the same problems in the SSL in the most scenic spots. We have already had plenty of posts on this board about people tying up space unfairly where nobody was sitting. Didn't seem like anyone had a good solution for that. Heck of a lot harder to deal with seats taken by actual passengers. A single SSL is not sufficient for the few hours of peak viewing times on certain routes every day, but probably could not be economically justified for its added cost over the whole route.