I am not very good at kiteboarding but have been surfing for a long time.
I have only seen the Celeritas in photos but the tail area looks wide for the board size and as it is super fast there probably isnt a lot of rocker through the board.
This will tend to make the board surf flat and fast but slide more than a board that has less area and lift in the tail.
Most quads, fishes and twin fins have a similar wide tail, which generally will slide in a big bottom hand turn. The thruster setup tends to hang in more and you wont see many surfers riding the other three setups in larger surf where they want that big bottom turn.
I would play around with a bigger fin combination, you may just need a larger centre fin. The local surfboard shop should be able to give you some idea, but believe me there a lot of theories about fin size and flex combinations