I think the mini is the perfect size for your little one.

I think the smallest carrier your dog comfortably fits in is usually the best idea.
I will say I have giant beasts (10 and 12 lbs), and we have the size medium Uncle Monkey. It had to be turned onto its side to fit under airplane seats, which I hated. My absolute favorite bag for air travel now is the size medium Sherpas. Go figure it's the cheapest and lightest weight of all their carriers too.

The weight of the carrier is probably more noticeable when your pups are much heavier like mine are. Since you are getting the mini, I don't think you'll have the issues with seat clearance on airplanes though.
Here is a picture of Lane, 10 lbs, in the size medium Uncle Monkey.
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Just for fun...can you spy Rory's nose? She was wondering what the hold up was waiting to go through security.
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