Thanks for your reply. Sorry I cannot comment any further about your intended jumps from 10.0 to 7.5 sail (I don't have a 7.5) or from 9.0 down to 6.3 sail (I don't have a 9.0) althought the last option is stretching a bit the sail range with a few or no overlap I'm afraid (it's fine to jump down to my 6.6 sail once my 8.2 sail is fully overpowered in a solid 15 knots).
Forget about using Kombat 96 with an 8.0 sail, the board is for sure too small. I've tried Kombat 95 with a 6.9 sail and it was fine, so 7.0 is max sail you might use on such a board.
From what you told us, it looks like Futura 122 might be the best combo to par with a 9.0 (+7.5) +6.3 sail quiver and then switch over to Kombat 96 +6.3 sail combo. However, to do freestyle tricks in 8 knots winds with a big sail and a large Futura, quite honestly, I really don't know whether or not it's utopia or fun to do, so I'll leave that to Taty and others freestyle experts in the field, sorry about that.