RE: kombat 97 fin sizes
Regarding using a bigger fin on the Kombat 97, I noted that Starboard shows a fin range from 22-33cm. So, in contrast to DavMen's recommendation above against going with a bigger fin, I really think you have something to gain by experimenting with a fin in the 30-32cm range.
At minimum, it's of value to think about is fin planform, as one can often leverage benefits in a stout low aspect fin that offers a bit more lift. For example, one can see quite a bit of difference when comparing onshore wave fins with down the line wave fins. I have a 24cm weed shedding wave fin that I sometimes match up with my older slalom board when sailing in waves with heavy kelp and eel grass, and it's surprising how well it works. It loosens up the board making it bit more surfy without affecting windward performance. In comparison with my classic slalom fin (a 34cm Tectonics Goldwing), the 24 wave fin is a tad bit slower, but it offers very similar power and direction upwind. In reality, the two fins are about the same overall area. Fin size, as expressed in length only, is only part of the story.
Another thing to keep in mind is one's weight. The demands that a heavier sailor puts on a fin is greater than a lightweight sailor. Folks realize this difference more readily with sail sizing, but I often think they don't see a similar relationship with respect to fins. Given the fact that the Kombat uses the US finbox, there are fin size limits to keep in mind, but I seriously doubt that you would have a problem with the slightly bigger fin sizing that you're considering. In reality, I would expect that you will be very pleased with slightly larger fin on your upper sail range for the board.