I do not know what to say about the different fin recommendations...... Remi Vila is a big guy, he sails 8.0-8.5 NCX in very different windspeeds than I sail my 8.5 Sailworks Retro or 7.8 NX Slalom.
4 cm is indeed a difference, but I think if you were trying to get going in slightly underpowered conditions, many sailors would up the fin size to 52 cm in a heartbeat. If they are fully powered to overpowered, they might want the 48 cm. If they were grossly overpowered on a 7.0-7.5 m2 rig they would most likely want a 42 cm.
For your 9.5m2 rig a 52-56 cm would probably be the best...again, it depends on the sail, rigging, the wind (over/under powered) and the sea conditions.
Your 39 cm slalom fin will most likely work on a 5.5-6.5 m2 sail range, which is getting on the small size for the Fu 133.
Hope this helps,