Hi Paul, I've searched around myself and my settings (for about 85-90 kgs) are as follows:
I use the s-type 104 2007 wood with a Techtonics FalconF1 36 fin with RS4 7.2. Love this combination, it's very fast! For earlier planing I can use a Drake slalom pro 36 cm. But this combination gives me less speed than the Falcon does. I've been told on this forum - by a SB crew member- that a 38 cm should also work.
Do use the RS4 6.2 with Drake slalompro 32: great too. For RS4 5.4 I stick to an 28cm but not very happy with this combo, the 28 seems to small. Trying to find me a nice 30 cm for the RS4 5.4.
About the recommended max sail size, SB's wonders me too. My suggestion is that the s-type, as set in the market as a crossoverboard, will for most users be combined with a powerful freeride/ superx sail. In that case 6.5 is a lot of sail. But for more raceoriented sails, a bigger size works well.