SportCraft TX350 Treadmill Safety Latch

I'm a complete n00b but I needed this for my TX350 treadmill and it actually works! I taught myself tinkercad last weekend and came up with this. Please forgive the imperfections, I'll probably rework it when I actually know what I'm doing.

This needs to be slightly flexible. I used PETG but I assume ABS should work just as well.

NOTE: Now that I have a clue I uploaded v2 which has smoother edges and a better fit