How about just rendering your lightning out with an alpha channel and importing it into Red? If you need an alpha channel you may prefer to use Advanced Lightning which will generate one automatically. Otherwise for the basic Lightning effect you’ll need something like Knoll Unmult or FAN’s Xmult (free download – do a google search). Either of these will create an alpha for your lightning.
JD
John Dickinson
Motionworks
https://www.motionworks.com.au