I love that you rode to Costco, Sky King! We did that recently too. We didn't need too much, which helped. I had a backpack, and my DH had his Arkel Tailrider on the rack, plus extra stuff under a cargo net and bungees. I don't think many people in Kansas City ride to Costco, but we love being different. 
Normally we are getting way too much there (including a case or two of beer) to ride, but this time it just worked out.
Attachment 16763Attachment 16764
Emily
2011 Jamis Dakar XC "Toto" - Selle Italia Ldy Gel Flow
2007 Trek Pilot 5.0 WSD "Gloria" - Selle Italia Diva Gel Flow
2004 Bike Friday Petite Pocket Crusoe - Selle Italia Diva Gel Flow