Thanks Tridge.
Yes I found your parameters on your FTP 
But even with this, not really good … In flight it’s different but when you are the ground even with proper calibration, disco show wrong direction (around couple of degrees : 15°). I move from 3.7.1 to 3.8.x and don’t find any improvement on mag with disco. I will try in 2 months, I’m far away to disco at this time.
Do you know why sonar is not working on Disco ? Is this related to this : Optical flow is not available in the new version firmware ArduPlane 3.8.1-dev
Main advantage on Disco is lightweight frame and standard reverse thrust support but could not be enable. I tried with joystick support, not RC so could not adjust some parameters, I will try with Sbus … Or do you have recommandation on reverse thrust with disco ? Does esc support reverse thrust on arduplane ?