The 15K unit is only 11% larger than the 13.5K unit. 100 degrees is pretty hot, especially for a hybrid.
Suggest PUGS ( PopupGizmos
) for the bunk ends and Reflectix (https://www.lowes.com/pd/Reflectix-5...5-ft-L/3011904
) for the bunk windows.
Also, if your unit is ducted, make sure that the openings from the cold air plenum into the roof ducts are fully open. They weren't on my Mini Lite. I got to mine from the top and opened them some more, but I really need to drop the inside grille to get to them properly.
Here's a pic down the duct. The light on the right is coming from the opening into the cold air plenum.
Here's another pic after I opened up the hole some. You can see the light it a little bit brighter and you can see the foam I cut out laying on the bottom of the duct.
The attached installation manual may not be for your exact model AC, but Fig 1 shows the openings from the cold air plenum into the roof ducts. They are the hole they call "Supply Air Ducts." You'll also see a rectangular "plate" called a "Duct Divider." Make sure this is sealed all the way around. It's the only thing between the hot return air and the cold supply air. If there are leaks, you're short circuiting the air flow.