I have an LS-8. I had a Mandle Air Extractor installed on my aircraft
after reading all the comments on the DG website. DG bought the
rights to produce the LS-8. Of course, to purchase the installation
kit I had to join the maintenance program and still pay significant
money for the parts. Then having it installed cost more. The Mandle
is installed on the bottom of the fuselage just behind the wheelwell.
The device made virtually no difference in my cockpit ventilation or
noise. BIG Disappointment.

Then, I bought the Butler vent and had it installed. It is installed
on the top of fuselage just behind the canopy. WOW. I can feel air
moving past my ears while flying. The canopy vent does not pop open
at high speeds. There is virtually no noise. This is essentially the
same type of vent that Sisu1A is using. It was worth the effort and
money. I can't tell you if it improved my L/D by 5points or more, but
the movement of air through the cockpit is greatly improved.

Guy "DDS"