The stock radio IS a double din already, so the mounting is all there in place.
The toughest part of all of this is the dash trim around it. If you've taken it apart yet, you know what I'm talking about... All the AC controls etc are in the trim piece that comes off to reveal the head unit.
Either modding the stock trim, or remolding is the only true way to get it done. Maybe making the entire thing 2 pieces.... hmmm.
Gotta be hella expensive to order a replacement part for that trim piece
All in all, that is fabulous work. Good job !