Hi Max,
There is a Triangle next to a 5-Gon, you can solve that by Merging the red Vertex to the white one (or the other way around, or Merge at Center..)

Do this on both sides and on the inside as well.
You can Edge Slide the holding Edges at that corner if you find it too sharp, but for the rest the model looks great to me.
I would however bring down the Level of the Subsurf Modifier to 2, that seems enough to me.