I used PA74 2004 to 2007 and my weight is 81-83 kg like you for 1.85m. Personnaly I used middle position for front footstrap and back position for back footstrap with a stance of 47cm if I remember. I think biggest sail you can use is 5.0 on the PA74 07, 5.3 is to big I find.
I used serial drake fin 22cm with 5.0 (blade) and a MFC 2K 20.5 with 4.2 and 3.7. 2k is really a great fin I love it.