I understand that you're comparing between the 2013 version and the previous version, but regardless of this I think that your 9.6 is rather small for your weight in marginal conditions.
I'm 87kg and I use a 10.9 with a 64cm fin in these marginal conditions. It still makes a difference of a few knots earlier planing c/w my 8.8 sail. I compare my 8.8 with your 9.6 regarding our weight difference.
My 8.8 starts planing from +/- 11-12 knots while the 10.9 starts from 8 knots, almost no pumping.
With my 10.9 in marginal conditions, I also put my mastfoot all the way back. For me it makes a considerable difference.
Anyhow, I also heard from some friends that the JP SLW starts planing a bit earlier at the expense of the "slalom feeling". It's like you said, you can't have it all in 1 package.
IS87 / IS101 / IS122 / US147