Hi Leon,
Longer subs would be better if you could?
My attempt was with 6min subs at 800 iso @ f/5.6
I have noticed that you have lost a lot of the reds and thats the Ha from the pencil so you would need much longer subs with your unmodded camera.
That 20D would have been ideal for this..
I don`t know about the red bit in the full frame if its some emission neb or another part of the Vela supernova remnant.
I can post a pic of my attempt if you want a look!
cheers Gary