I dont know about the big ones, but my personal experiences (78kg) are:
But going from 7 to 11 or from 6 to 9 does definitely NOT work at all IMO
Which are about the same steps you have now, percentagewise that is...
Even the 5-7 is a bit big sometimes, so some got 5-6-7 to cover better (we ride often with these sizes in waves).
So would aim for something around 33% change in size.
Regarding the big ones, things change dramatically.
I prefer a small change in size around the "good" max sizes, which for me is around 11-12m2.
Above that (with my weight), it does not matter if a small or a huge step, as they are so slow and not the same "art" of kitesurfing no more - so much more an individual preference, and a huge step in size makes more sense here, in these low windspeeds.
Just my experience