I did a similar mod so thought I would share what I did. I'm not crafty so it's a little messy, but it works perfectly. I cut a hole in the existing roll-down flap, then used hot glue and double-sided bias tape to attach it. If I were to do it again, I would hot glue the mesh directly to the inside and glue bias tape on the edges outside to give it a finished look. I tried to get a pic of her inside with the flap down but she's black and gray so you can't tell she's in it. I'll probably add a couple very small mesh cutouts at the top of the bag. Took about two hours since, again, I am not at all crafty so went slow because I was convinced I'd ruin it. It hasn't been long enough to know how well it holds up but my dog is pretty chill and it seems very sturdy. Happy modding!