Jay
Have you tried this web site or it's contacts. It seems they could give you better advice as to a promotional Q500 class. They should be will versed in the European Q500 classes and the availability of good and preferred engines that meet the rules.
http://mcbssy.free.fr/
Good contacts in Germany. They fly in races in France are on a pylon forum on this web site. If you don't speak German English well be fine.
http://www.rc-network.de/forum/forumdisplay.php?f=75
On this next site you can get a lot of info from this gentleman. He makes kits and I know a sells a lot of them to French racers.
http://www.attackjack.eu
Any of the people in the above forums can put you in contact with pylon racers in France.
I hope I didn't misunderstand your request and you are just trying to find out what we use and why. In any case I would add the Webra 40 GT. And separate out the Rossi 40 23R sense it comes with a tuned muffler stock as may a couple of others such as MVVS and OPS.
Denis