My Mom's office needs some sort of cooling. She has a portable AC unit, but it just can't keep up with the Florida Summer, even on full blast.

Really would love to put a mini split in, but just don't have the $3,500 it would take to get it done.

The office has side sliding vinyl windows with a pretty tall bottom lip (picture below). I got her a window AC unit designed for this casement windows (Frigidaire FFRS1022RE).

Problem is that I'm concerned about how to install it in her window...

Window Photo

I was thinking of building a wooden platform for it to sit on and bridge the window sill (as opposed to using the included mounting bracket) but don't know if that overcomplicating things. Would appreciate any advice you can offer.