Nerf has now uploaded this vid to their Youtube. Pause at 0:49 and 0:50 for what looks like the full Hailfire. It looks like 2 magwells to me. What do you think? Post in the comments!
Thanks Milez_Is_nerd for the link!
Edit:Nerf has taken the video down. Check out Tactical Tag for screenshots of the Hailfire and Neo Creations for a drawing of what he thinks the Hailfire looks like.