Great questio Daniel! Let's wait the "big guns" to answer!

I have an idea about this, but I'm not an expert of the aero field. Let me try to explain that...

I think by raising the thrust line the designer tries to split the fuselate side area in two parts (up and down the thrust line) such that these two areas are equal.

Why? If the spiraling prop stream is centered on thrust axis (which I think it is true), then by doing so the plane will require much less right thrust (at the limit of equal side area up and down, you could end up with no right thrust required)

But now let's wait an opinion of some expert...