No, no, no, not all 3 side-by-side. A stack of two next to a single. Like this: = _ That should fit. Also, I think the PDXs might fit in the storage area where the spare is on a 3er. I'll have to do more exploring, but you might even be able to get one upright against that back wall.
The option for the changer trim would be a piece of cake. I'd go that route if I hadn't already made my enclosure and it won't fit with that side piece.