Oh Tucker, I see you make sure you line up the rear legs first on that pesky heater vent! the better to kick it back into place when it tries to escape, huh? Let mom take pictures of you a bit more often, you are SO lovely!!!

My cat napper used to pull away like that as well. I finally pulled it REAL snug and gripped it with the velcro which holds the whole thing onto the windowsill. It hasn't moved in almost 7 months! Might want to give it a try.