Very interesting configuration. The first thing I noticed was the
oversized surfaces in the tail. The second thing I thought was "But
there is no motor, why the heck is this thing solar in the first
place???".

Only then did I notice that the motor was in the tail (I was looking
for the standard boom mounted unit). So that has something to do with
the overrsized tail surfaces. Aerodynamic or structural or both?

But what is the advantage of the motor in the tail? I can think of
one disadvantage - you can't retract it.