After some search, i found this:
"The story behind it is a EO Convert friend of mine was making fun of the way i crossed myself all the time when we prayed. One time in the presence of an EO priest he told my friend to stop 'cause my way was actually more ancient (whatever that means, as if it mattered to our Lord, anyway). His version of the story is that the Eastern Orthodox, who were heavily offended by the presence of the crusaders in their lands, agreed to start signing themselves in a different manner so as to be visibly distinguashble from the 'western oppressors'! LOL
anyway, will attempt to find all possible litterature ASAP for you, Ben.
yours in Love,