I find it amazing that there are not more pilots flying the Diana-2 at
the worlds, since it seems to be head and shoulders above anything
else in the 15M. I guess too many pilots do not like the side stick or
lack of manufacturer reputation. Maybe the Australia fiasco stopped
many. Or are there other negative factors?

Other than that, I can not think of any other reason to pass it up for
a competition. If it were a new unproven design I could understand,
but it's not new and has already won a boatload of competitions,
despite flying in so few numbers. They always seem to clean up no
matter the competition.

Or is it that people buy what everyone else buys kind of thing?

I also think that the ever increasing wingspan in the open class has
reached a point where more does not mean necessarily better. Granted
the EB29 is leading, but look at the daily score sheets and the
performances seem so close, it's just very marginal from one to the
other. I think new materials and new structural designs to save weight
will give better results in the future, judging by the Diana-2
approach in the 15M class. Less weight = less required wing area,
higher aspect ration of wing, etc...

Feel free to discuss, as I don' see many discussions on sailplane
performance these days. It used to be a hot topic.