We have IP dect set up on a 412 at 4.1.9 with seven RFP32 base stations. The system ran fine and we added seven more handsets over the last four years with no problems. Due to construction we need to add at least four more base stations and are slao planning an upgrade to 6.1 shortly. I need direction as to how to proceed adding these and what type to buy as I am getting conflicting information from our distributor as what to do. Will the new licensed basestations work with the old, do I need an upgrade kit, etc. Any help would be much appreciated.