I made it of ABS with 3 perimeters and 20% infil, it is solid for the joytrainer mini, and has good elasticity, the weight of the plane is around 650 grams, if it needs to be more resistant you can add a wire in the center you will find a dedicated place.

For the wheels I used m4 screws with nuts to secure them to the landing gear, and then a self-locking nut to secure the wheels.

edit after the real use: It worked really well, i made some great landings.