I guess it depends on whether you plan to keep your Naish 8'11" 104 liter or not.
Then it depends on if you want more high wind capability or more low wind capability.
If you want more high wind capability (and it seems like you do since you want to sail 4.5 conditions and you weigh 120 Kg. (264 lbs.) I would suggest the Futura 101.
I do not weigh anywhere near what you weigh, so I'm guessing the Naish 104 liter is a bit of a sinker, right?
It's a tough call.
A little earlier planing, or a little better high wind performance.
If your Naish is already a "sinker" then the Futura 93 or Kombat 96 would be more
suitable with your 4.5 rig.
Hope this helps,