Thank you guys for your help, I really appreciate it !
I have done what you said and started from a working file. I have taken the template.tmd file from the aircraft workshop, added my geometries, and added the aerowing definition from the asg29 glider. It doesn't crash anymore, which is some good progress ! However the dynamics are very unstable, so I will have to tweak it that so that the hangglider is actually flyable...
For the flight dynamics, I thought about controlling the hangglider using weightshift, so that it is as realistic as possible. The setup I thought of is having a rigidbody (the pilot) connected below the fuselage through a linearjoint which can be actuated by the player. I am not sure whether this is going to work, since nobody really did that before. Anyway, I will experiment, and who knows, maybe it's gonna work.
I attached some screenshots of my model (to tease you ), which I am very proud of. I have made it myself using Blender and GIMP, but I haven't added specular and reflection maps yet.
I will keep you updated if I manage to make some progress. Cheers !
You can use two joint_multi or one jointlinear with two axes of rotation.
Both methods should work since you can actually change the center of mass by moving the pilot body.
E.g. the CG of the P38 moves significantly as the gear is retracted in Aerofly FS