I have 2 control joints right near where I need to put 1 of my columns. I was reading on greg smiths page and it said there should not be an issue.
http://webcache.googleusercontent.com/search?q=cache:npJSVThIjfcJ:www.gregsmithequipment.com/2-Post-Lifts_3+&cd=1&hl=en&ct=clnk&gl=us