My window slides, but I never use it since there is no screen. My truck does not have a slide window. I think the TC slide is to get access to the truck, but not many owners will crawl through and fewer want to put weather seal between the two and rub off all the truck paint. "Leaks" is a lame excuse, in reality, few want or need it and is a feature that is near the bottom of the list and a good place to save a few bucks for something few use…
The smaller btu AC is a good move, TCs have such small cubic feet that it takes little to cool them down. My 9,200 cooled TC down in minutes in hot summer and compressor did not have to cycle that much.