I don't have the 1200, but I do have a Durst 138S and here are the condenser set ups for the different film sizes: The curved sided always face each other towards the middle.

Film size : Lens : Condensers

24X36: 50mm : 130 over 85

6X6 : 80mm : 200 over 130

6,5X9 : 105mm 240 over 130

9X12 (4X5&quot 150mm 240 over 200