Funny that you should post this today. I - just now - came here to find out the answer to the same question. Looks to me like the new Sixt location is right next to Costco (which is good for me because I stop there on the way in anyway). I've been to that spot as a result before. It probably is a solid 10 minutes from the airport. Don't know how often they run those shuttles that far - that would be my concern/worry. If they run them just as frequently as the other companies it should be fine. Would be great to hear from someone who's actually done it!