Attaching punch bag bracket to pebble dash exterior wall
Don't do it!  

Former boxer here.  I put up a mounting kit in my joists in an apartment I had in college...  I split both joists it was mounted too.  I was using a 100lb water bag and weight makes a huge difference.  But I don't care if it is 25lb.  Don't do it.  

Buy a pole and mount it to that and they sell punching bag stands.  The link isn't an endorsement, just an example.  Also if you mount it to your house you will have probably only 60 degrees of hitting - 30 on each side given you don't want to pop the bag directly into your house each time.

Note that you are probably attaching this to wood.  Assemblies like this are not supposed to go into wood - needs metal.  You screw this into wood and the constant reverberation, up/down/side forces will slowly make the screw hole bigger and they will eventually wiggle out over time - for sure.