Apr 6, 2017 - 3:43 PM
Welcome to MySwissAlps Dean!
You might be right that there's no airco in these trains, but I am not sure. There is between Luzern and Interlaken. I haven't heard of temperature issues yet. The section with the VIP seats is less than 2 hours, and you can move around in the train if needed. I'd take a cool drink and sunglasses and go for it. If you have a huge amount of luggage you may need to place it elsewhere in the carriage, so a lock might be a good idea.