thanks for clearing up some of the info..
1 Champ is a 3 ch plane for beginners. all you have to do is give throttle she will climb. get off the throttle she will land herself.
2. champ is for dead calm days, and can be flown in gentle breeze, the more the wind, more the challenge.
3 trimming her in dead calm weather, and not at half throttle, but coasting speed. a little down works for me.
4. battery placed in will change COG (center of gravity) once you find cog, with bat. mark the bat and planes bat tray a line will do, each bat you use bigger or smaller.
5. inspect rudder & elevator for any hair line cracks, especially by the horns if you are going off trim. even check your Tx for the correct trim...
I read you moved forward had some good flights and quickly learned her. no crashes. soon after you crashed, and now you want to move to an better plane?
What Transmitter are you using? once again?
The Sport Cub S, will be a stronger plane, easier plane to fly over the champ due to the SAFE technology. I would not get the Radian just yet I feel it is a great plane yes but more a glider than a plane. are you interested in using less motor and more gliding, it is a Lighter plane and some more care is needed.
If you want to get a plane the next size up should be something to look at, but if UMX micros are what you like flying. Sport cub SS, Carbon Cub SS down the road,