I view all Gainer tricks as Aerial Variations that are swung into. And the Gainer Arabian is no exception.
You can easily turn an Aerial into a Webster by tucking your legs in. You will also face forwards after. So if a Gainer Flash is just an Aerial that is swung into... then all you need to do is tuck in and "Webster" it to turn it into a Gainer Arabian. Look how this Aerial Webster looks like. Pretty much the same trick as my Gainer Arabian, just with a different takeoff.