I have a Scubapro FFM too, fitted with an Apeks reg. It is important to have a rig with easy acces to the tank valves. Either Hog/DIR with twin tanks and manifold or an inverted (worn upside down) single cylinder with a cage protecting the twin valves. There are other configurations as well, such as sidemount cylinders. The idea is to have redundancy and easy access to one's valves. Being able to shut down a free-flowing reg on my own has practical and psychological advantages.
When experiencing a free-flow it usually does not start violently. You shut down the valve, take the FFM off while already holding the secondary second stage, enjoy the shock of the sudden icy water, breathe from the secondary, find and put on the spare mask, then clear it. This is no substitute for a FFM certification, lowviz is right about taking classes.
The intermediate pressure of the first stage and also the second stage have to be tuned by a professional to work better in cold water, the factory setting isn't always the best.
One of the main causes of free-flows is the humidity of the air that makes it through the compressor filter and into the cylinder. Upon demand, more humid air generates ice at the expansion point - the first stage. Having a well-serviced compressor and good filters, even the addition of a personal filter can help to avoid free-flows.
