I'm researching dog doors and have confused myself. There are automatic doors from $50 bucks to $800 and none of them get good reviews. There are "weatherproof" doors that look like they just have double flaps--which open and close together once the magnets get stuck together. There are doors with a six inch tunnel in between and two flaps... but will tiny dogs be able to get through it? I just want a nice, draft proof safe door for my on the small side Miniature Schnauzer. Has anyone found anything that really works well and doesn't let all the cold air in and warm air out??? Thanks.