Hi Sanctus, sorry to cut in on a SB team question.
I'm 105kg and 194cm, I have used an 11m Warp on both the iS144 and iS150. No real benefit in going bigger than a 10m on the iS144.
The 11m worked like a dream on the iS150 and felt like it would easily take a slightly bigger 11.5m/11.9m.
I also used a Deb R13 64cm soft on a super light wind da and it was fine. 56cm/57cm would be the bread and butter main size though.
The iS150 will be a really good replacement for your FF158. C/W the iS144, the iS150 feels much bigger than the numbers suggest, it is as stable as a formula board (the iS144 is not, as it feels much smaller).
Here's a link to a recent discussion on big kit, some of the comments might help you decide.