I have a Kombat 97 inbound... but I was thinking if I could push it even more, by getting a NP Excess 6.9...
Having been accustomed with a 2001 Carve 111, stock freeride 32 cm fin or freestyle 25 cm fin with a 6.9 sail combo, I've tested a 2005 Kombat 95 with a NP Jet 6.9 (ancestor of current Excess 6.9) sail and either a freeride 31 cm fin or a wave onshore 23 cm fin. I didn't experienced any problem, mainly because the OFO width is about the same at 40 cm as that of the 2001 Carve 111.
Now, I'm using since 18 months a 2006 Kombat 86 with my Jet 6.9 sail, either with the stock 30 cm freeride fin or with a wave onshore 23 or 24 cm fin, all with great success and fun. For my 65 kg, the Kombat 86 felt much nicer and more lively under foot than the Kombat 95, surprisingly even with the 30 cm fin and 6.9 sail combo.
So with your 75 kg and Kombat 97, I can't see any reasons why it shouldn't be as nice and fun as it is for me with the Kombat 86...Go for it !