I recently built a ROFI but since I bought the cheapo SR04 rather than a Parallax Ping sensor, it didn't fit in the front body panel holes. So I took the original file, patched the holes in Open Scad and cut new ones. I made the scad file parametric while I was at it just in case someone else wants to change it for some other cheapo sensor they might find online. I didn't add any good way to anchor the sensor to the body panel but the original file didn't have any way to do it either. You'll need to download the body_panel_front.stl file from the original project to load into the scad file.