Another thing I’ll have to look at is a way of locking the landing gear when it comes down.
If you look at the video you first posted,
You'll see they rotate the legs down past the vertical, so that any downward force on them pushes the leg back up the opposite side of the legparked/travelling position.
Some sort of block stop near the top of the leg, perhaps on the frame mounting where the leg rotating/pivot shaft is, will stop the leg collapsing