hey!
the weight difference to a 10S lipo setup is between 350 and 400 gramm !!! for f3a pattern class this is a lot and of course the aircraft handling changes a lil bit. also every aircraft have a different way to react on a contra prop system and this less weight. in the end must make a test bcs before you never know and is very dependent of the pilots flight style. but i can say that with me and my oxai beryll08 (4,6kg) works amasing. now i will build up a oxai axiome and see if works there in the same way or maybe even better. i can not imagine but as the base aircraft is better...............can be.
in the winter i will also add the aerodynamik modifikation package of the asyuler eternal on my beryll, and im shure that than i will reach the highest level of flight performance i ever had on a single wing f3a plane! :-)
nice flights, bye, bye,

dominik