Success !!!!! (Almost .....)
First flight : Direct to the ground :-( .... I was alone, so I launched it by myself but with too little strength. Fuselage broke near the nose, but after some glue it was ready again in 10 minutes.
Second flight: I trimmed elevator up and launched it again but with more energy and more angle and ... IT FLYES !!!! Beautiful flight of almost 10 minutes ... Power plant is ok, at full throttle it climbs easily, and most of the flight was at 60-70% throttle.
It trended to go down, so I trimmed elevator a bit more up. Once on ground I measured 1 mm of elevator trim up.
I noticed some "tail" instability, I mean, small and random lateral movements side to side. There was some gusty wind, perhaps it was that.
Wersy, what do you think? CG is now 28 mm, should I reduce or increase it to compensate for the nose down trend? Perhaps the lateral instability could be improved also by moving the CG ?.
I was also thinking about the winglets. I printed them in 0.9 mm, perhaps some vibration that causes that behaviour? I can try removing them next time.
Third flight: Shorter, because wind increased suddenly. During landing, and like a good Bumbble Bee it is, he went out of the runway looking for flowers .... Result: hard landing against a bush and leading edge of the center section broken (see picture). I glued the sections together during assembly (bad idea) so repair will not be as easy as "reprint and replace", but it is not as serious.
So, I am very happy !!! Despite the hard landing, it was a nice morning flying this nice airplane, and for me, it was coming back to this hobby after 20 years ...