Locking hinge between the top and bottom frame

I’m trying to mount the x4 on a skycruiser trike. While doing that I realized that the hinge between the top and the bottom is not locked and can move with some weight/pressure

To sit in the harness in the trike the pilots weight starts bending the top frame forward

I can’t figure out if there is any built in mechanism to lock the hinge. Do I need to stick some pins n the holes that I see in the picture attached? Or is there something built in that I’m not seeing

If you can’t find matching holes, the hinge pieces can be turned 180 the other way. You could figure out a pin to go in there or drill it to suit where you need it. There are also 3d printable hinge stops (check Gliderpilot’s build) you can make.