not sure about apba. this is what the lucas rule book says.
8.25 Kill Switch
All open boats must have an electrical ignition kill switch device which will immediately and automatically shut off the engine in the event the driver is thrown from the driver’s seat. All open fuel injected blown boats utilizing nitro-methane for fuel shall be equipped with two automatic kill switches - an electrical ignition kill switch as well as a fuel shut-off device. The electrical kill switch shall be mounted directly along side of or in front of the driver’s seat, and within an arm’s length of the driver. The automatic fuel shut-off device shall be installed in the main fuel supply line between the fuel pump and the injectors. Both the electrical kill switch and the fuel shut-off device should be mounted and the release cords routed so as to disconnect should the driver’s posterior move more than eighteen (18) inches in any direction from the driver’s seat. Any kill switch device that is attached to the driver must have a maximum breaking point of fifty (50) pounds within a maximum distance of six (6) inches from the driver.
I don't think the op was talking about circle racing. if he's going to run sdba or lucas, this is the rule he needs to be in compliance with.