best self-launcher propulsion system?

At the lower cost end of the spectrum, I can say that the rotax
installation of the Apis is very well thought out and has performed
for me over 4 seasons without fail for air restarts. It runs cool and
usually requires less than a minute at idle before stowing. The engine
is rev limited to about 6000 rpm and I don't always get that.

It is relatively idiot proof, (witness I am still here writing). This
particular installation is no longer available as AMS bit the dust.
The glider is still being built by Pipistrelle with a different
engine.

The Apis is not a state of the art high aspect glider but capable of
long cross country, have done 300k here in Oregon. The wing area is
large, keeping the loading down, and while I get only 5-600 fpm at sea
level, I still get a positive rate at 10k.

Vibration is unpleasant, and I am constantly looking for the smoothest
rpm range for the altitude, sometimes 100 rpm makes a huge
difference. Nothing has shaken off the bird yet and I constantly tell
myself, that it is at least as pleasant as flying around on tow.

Not sure what Pipistrelle is asking but I got in for about 1/2 what a
German machine would cost, including the trailer.

Mark