Monti - if you are after a 50/50 surf/flat water then I would go longer than 9ft 2.....paddling short boards on the flat isn't fun.....you go from side to side with a couple of strokes and it is SLOW. Get a longer SUP (10.5 plus) that you can do both with and still have the stoke
You are 80kg so I reckon Scarbs SUP has nailed it - 10ft 6 Fly (if you are a Fanatic man)