My Male Sneakers (3.5yo/13lbs now) slams through the Doggy Door like a Tank, but, when I got Becca (1.5yo/8lbs now) she was very timid about using it.
What I did was remove the heavy plastic Flap with the attached metal magnet strip, and taped a Baggie in it's place. That was VERY easy to move through, and after a couple days, I replaced the original Flap, and she booms through it now like it wasn't even there.
