Mattress Retaining Clip

I have one of the minimal bed frames made from square steel and a mattress on top. One of the issues that I have is that as I sit down or shift on the bed, the mattress has a tendency to shift around.

I designed these clips so that they'd fit over the frame and keep the mattress in place. I put a couple on each side at the corners of the bed frame. They're tall enough that even with me sitting in the middle of the mattress, the lift at the ends won't hop over. They're a bit over engineered, but I wanted something that wouldn't need to get replaced quickly.