Might sound odd, but could you get a couple of strong cardboard boxes weight them down with a brick (or something) put your plants to be hardened off in them at the lotti for a couple of days then the next couple of days take plants out and put back in for the night. Unless frosts are forecasted in my experience its the wind that does the most damage so protecting them from the wind in this manner would help acclimatise.
Only my take, others will be along with their ideas.