I have a 2 story house on a single Lennox unit. I am experiencing the typical "hotter upstairs than down stairs" syndrome. I am considering installing a Lennox LZP-2 zone system to divide the upstairs and downstairs into 2 zones. My unit is a split system heat pump with easy walk-in access to the air handler and trunk ducting. There are two trunk lines; one for upstairs and one for downstairs already. Anyone have a ballpark idea of what this would cost?