Update: I added an integrated holder for a Melexis sensor 1cm diameter. Could be modified to add other holders or change size. Add a laser, etc.
Yet another HC-SR04 Mount...But this one is very general purpose and low screw count. I wasn't happy having to use several different mounts requiring an excess number of screws so I designed this to be very versatile and simple and quick to install. It has screw holes for back plane mounting or floor and ceiling plane mounting. It can easily be held in place using just one of the screws for either option since friction will keep it steady in all but extreme conditions. There are more screw holes than you really need just because my pan-tilt mechanism had 4 holes for mounting stuff and I matched it. Use 3mm flush mount screws. Flush mount.
The HC-SR04 is held in place by tension alone but a clamp is provided for "high G applications". This can easily be a one-screw installation, or two if you use the clamp or 3 if you are worried about vibration from the rocket blast.
Used OpenSCAD and included the files.
NOTE: Be sure to lay the clamp sideways in your slicer when you print.