Eric Mc
Here are
some pictures of HD34s
tech data (in French)
F-BICV website (in French too)
The only aiworthy one is F-AZNH, formerly F-BHOO
wingspan is 46m (150 ft for the metrically challenged).
cruising (?) speed is120 kts, with a 12hr autonomy.
The idea behind the high aspect-ratio was to minimise induced drag, allowing for long cruising times at low speed, which is what you want for survey work.
The downside of that huge span is reduced yaw stability, hence the large and multiple fins.