I must admit having only experience in the installation of split, mini-split, and the normally placed window AC system. With that in mind I can't speak with familiarity to all the issues that a project such as your's might present. The fact that there is to be a 3 1/2 foot sleeve would make me believe that the actual AC unit would be at the conditioned end with the sleeve providing a hot air exhaust. -The alternative would require a long reach for the unit's controls-. There are two items of concern that were not mentioned in your post:
#1, How or where will the unit's condensate drain.
#2, Will the sleeve be large enough in height/width to efficiently accommodate any side vents the the unit's cabinet may have. These would normally be open to fresh air on the exterior. Contacting the systems tech support may be a cheap but valuable call to make prior to cutting a hole in the wall. Regardless, best of luck. I would be interested in knowing how your finished project performs on a hot and humid day, maybe even a photo.