You did find the stud 😉, I would just cut it and if you are uncertain you could back the drywall on the side of the stud. So cut a piece of 2×whatever you have lying around about 3-4 inches larger as the height of the catflap and work this to the side of the stud and put some screws in it... Should be sufficient
AgileCookingDutchie t1_j6i50jg wrote
Reply to Is it okay to cut out a small section of a drywall stud? by Wolferesque
You did find the stud 😉, I would just cut it and if you are uncertain you could back the drywall on the side of the stud. So cut a piece of 2×whatever you have lying around about 3-4 inches larger as the height of the catflap and work this to the side of the stud and put some screws in it... Should be sufficient