If you want to cruise/freeride with it in 18 knots average with peaks over 20 knots, you'll get your hands full.
I don't say it is impossible, but then there are more comfortable boards. A lot depends on the water state, i.e. flat or choppy. I think that the IS117 with a 6.7 or 7.2 sail will allow you to plane starting from 13-14 knots with your weight.
The IS117 is something like my IS122 and use it often with a 7.8 as smallest sail. It feels very sweet and it covers a very wide range 15 - 22 knots, but I'm 87kg. Me too, I'm not a competition racer but I want to blast as hard as I "comfortably" can. Usually I use the 7.8 on this board when this sail does not work well anymore on my IS101 because of irregular winds. When the wind drops below 15 knots average, I use a 8.8 as largest sail on it.
IS87 / IS101 / RRD114 / US147