I highly recommend that you videotape the discovery deposition of your opposing party.  At mediation use sound bites from that deposition.  This will alleviate the opposing attorney saying, "That is just his version of what was in the deposition".  It begins one of the objectives of your mediation, to get the opposing party personally thinking about becoming more realistic in negotiations.  Your mediator can now use this tool effectively, "How do you think a jury will react to that deposition?"