First off, even though you've a Travel Supreme, the walls aren't that thick or strong for any more than a very light one. You'll have to build a platform to fit your window frame tightly, with bracing on the outside to try keeping it all from pulling the window frame out. Don't think a little extra weight will bother the slide any, but I'd be careful about that window frame.
Why didn't you go for an indoor unit in the first place? We had our 15k unit fail last year just before we had to go to something we couldn't duck out of, and I got one from Amazon (https://smile.amazon.com/gp/product/B00HZKPNE6/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1), and cut a plywood piece to fit a window for the two hoses. The thing worked very well in 85 degree heat & sun. After we got back home, I got a new AC unit for the roof and the indoor one replaced a window unit in our sticks & bricks home.
