Your boat is designed with a righting moment, even the water ballast boats will theoretically right themselves after turning turtle. That being said, most boats heel to the level of comfort of the most timid crew before people start getting concerned. In SF Bay we regularly get the rail in the water due to the heavy afternoon winds but, can stay much more upright by reefing and using a smaller jib. if you keep the hatches closed while sailing, a complete knock-down while uncomfortable and wet will generally not be an issue.
One thing I've notice with many of my boats is that as I heel, the boat will reach a point at which it hardens and further heel is difficult. My Hunter 25 wouldn't put the rail in the water even in 40kts of wind due to its 4' lead keel. Your water ballast boat may be a bit more tender so may heel further.
All of this really isn't fun and certainly doesn't help you to sail faster - remember flatter is faster, if you go too far over your just dumping wind and the keel and rudder lose effectiveness.