I have been there a couple of years.
First time I took my 9m2 (and 7 and 5 of course), but never got a chance to use it, as it was 4-7m2 every single day, 12 out of 14 days, aside from two days without wind at all (and turned starport a few knots only).
Second time down there, also in the summer (January), I actually used my 9m2 a couple of times, out of the 14 days, and this time wind every day.
Seen in retroperspective, I could just as well have let my 9m2 stay at home, and surfed or done something else these 2 days, as you are always kitesurfed to "mashed potatoes" anyways, after being out every single day and evening for up to 8-10 hours if you want
So you need some rest eventually, no matter how fit you are
I weigh the same as you.
5 and 7m2 used about the same number of times down there in these weeks.
We might just have been lucky these weeks/years, as I've heard you can get lousy wind and conditions too
Havent experienced it myself though...
So of course a chance to omit the 9, but on the other hand, soooo much easier to pack and travel, as you need way less space in your trunk with only a 5 and a 7
It seems that either it blows "standard" - or it goes totally bananas with odd winddirections or no wind at all, and useless anyways (besides racing with huge kites maybe).
So you could bring your 9, but forget about bigger ones...
Or take the chance and go without - as IF it is not sufficient wind at CT itself, you just drive down to Witsands, Scarborough, Platboom etc, where there is much more wind normally.