Not too suprisingly, when Ifly anything CDI equipped, Iuse a Tech-Aero Ultra IBEC. You don't get any filtering of CDI noise unless you take this type of approach.

Also, with the IBEC, you get a considerable advantage over an ordinary regulator since you can configure it to match the CDI voltage requirements, and it also is designed to properly accomodate the deep current impulses that CDI's impose on their supply, and it does so without there being any ill effects on the receiver side supply bus. Another thing you get is the ability to control ignition on/off from the aux channel that the IBEC plugs into, also allowing failsafe responses. You don't get any of that when you either tap directly off the receiver bus, or use a non-purpose built regulator. Basically, the way that the Ultra IBEC is designed, it just lookssimilar toaddinganother servo to the receiver and its battery supply. To the CDI, it looks like a constant voltage battery that can deliver the current it needs on demand.

To be clear, it is still fine to use a single, or a redundant set of regulators between the battery or batteries to supply the entire system, but not a good idea on the CDI side. Unregulated battery supplies such as A123 or 2S LiPo direct to the receiver bus are fine too if your receiver and servos can handle the unregulated voltage.