Broken Mounting Posts

So both parts need a way to be rebuilt, and the goal is also to use metal threads and machine screws.

For the posts in the body, the idea is to make a replacement piece with the threads in it. Here's a helicoil set that will have the desired 2.5mm x 0.45 screws:

Now you stack 2 of these inside the replacement 3d printed post/splint. This will give you plenty of thread for the screw, but more importantly handle the stress of the tightened screw in the helicoil, i.e. spread the stress out over more threads in the plastic.

For the chassis, we need to come up with new posts, which will be printed with a flat square flange, which will have to be trimmed on one side (or we just print 3 sides of the flange and leave one side flush. now you screw this in place from the chassis underside with countersunk screws. It's now securely fixed to the chassis.

The last item to be solved is to put the bearing surface for the screw head in this tube. Ideally a molded in washer would do it, although there's not enough diameter of the post to hold the washer and of course how to embed a washer into the printing.