iSonic 86 Sail Sizes

[Haggar]

I have a 2008 i86 which I use for GPS and I love this board. I use this board with RSR's 5.8 and 6.7. I'm looking at changing to RSS Mk III"s but the sizing has changed. I weigh between 75 and 80 kg(depends on beer consumption for that week) will the 7m be too big for this board, am I better off getting the 5.5 and 6.2 or the 6.2 and the 7 ? The RSS's should have more low end grunt then the RSR's

My other combo is a i122 and RSS II 8.4 and I am a bit worried that the gap between both combos will be too big if I dont get the 7m. My main goal is GPS speed, but dont want to be sitting on the beach either.