The ground plane under the visible part of the patch is an integral part of the antenna and should extend for some distance beyond the visible patch. This can be either more of that double sided PCB or structure. (Changing the extent of that ground plane alters the center frequency. Fortunately, after a certain point, adding more doesn't change it much.) Lots of patch antennas are mounted to conductive structures. One example that springs to mind is on the nose of flight test versions of the
ATACMS Block II. (Visible in pictures as a dark band on the light nose.) That had not one but three patch antenna systems to cover C, S,and L bands. (5GHz, 2.3GHz, and 400MHz)
Adding a patch antenna to a payload section is not simple. You need multiple patches and the simplest way is to fab them as a single wrap around PCB. But for aerodynamics the top of the antenna radome should be flush with the surface of the airframe. Which means you have to cut a band out of that CF airframe to create a recessed area and have structure for the antenna to mount to. Repeat for any additional antennas.
Designing and building these antennas is both a science and an art. The science will get you close but because of various details that are difficult to model (the radome for example) tuning the antenna is an art. Requiring test equipment and a sharp knife.