Pylon self-launchers fall into 2 groups:
(i) DG400/PIK20E/DG800A/DG600M types where both the engine
and the prop and mast are sticking out into the airstream.
(ii) ASH26E/DG800B/DG808C types where just the prop and mast
are sticking out into the airstream.

If I recall correctly the DG400 certification required that DG
demonstrate an engine stopped and erected plus full air brake
landing. W Dirks (the D in DG) performed this but suffered some
minor back injury. (Well this is what I was told 30 years ago when
I first flew a DG400, I can't vouch for its accuracy).

So the advice was always to have NO air brake extended during
the round out: the sink rate with extended stopped engine is
pretty substantial. The other advice was to very aware of
turbulence from the stopped engine masking elevator feel.
Dave Walsh