Backpack for carrying a smallish dog? K9 Sport Sack?

Someone had a thread about a backpack for kids, and it got me thinking I need something to carry one of my dogs who has a bum lag. She's a Westie so ~ 23 lbs. She's a bit big for all the backpacks we've seen in the pet stores, but we found the K9 Sport Sack online.

Has anyone tried one of these and are they decent? I'm in Canada so it's a bit of a risk if it doesn't work out.

Any feedback on them?

Thanks.