That’s not possible. That would mean you have a negative prop slip.
Even with a super efficient setup and a very low prop slip of 7% you should use 3500rpm to get to 30kph.
Do you not mean 3600rpm which would give you a prop slip of 8.3%?
I’ve hit 38kph on the 120kv with 12s and FR prop a few times. It seems to pretty much be close to the max speed I can get it with super fast and efficient foils.
I need to build my pack up to 14s at some stage and also modify the shaft of the 100kv to take the FR prop.