(Sorry Roy, casting for Tucker and Dale vs. Evil 2 is down the street.) Leading into his UFC 137 bout with Mirko Cro Cop Filipovic, former IFL heavyweight champ Roy Big Country Nelson has enlisted the help of former UFC heavyweight champion Frank Mir to prepare him for the Croatian legend. Mir, who defeated Nelson by unanimous decision at UFC 130 back in May, also holds a knockout victory over Cro Cop from their headlining bout at UFC 119. Nelson explained his decision to bring in Mir during a…