I always use SPS by Bakery Crafts for large or heavy cakes and they work great. I took a five-tier cake down the roughest road in the county and nothing faltered. You can find them here at GSA or just Google Bakery Crafts SPS.
http://www.globalsugarart.com/cat.phpcid=887&s=&name=BAKERY%20CRAFTS/Bakery%20Crafts%20Pillars%20&%20Plates%20-SPS%20System%20-
