This model has received a lot of hate on the internet but I REALLY like the way it looks when it's all put together. It builds really well and is pretty easy to magnetize to use it for either variation.
To do the Vengeance version I just put magnets on the sides of the turret where the plasma cannons go and dropped in a magnet on each cannon.
For the Dark Shroud variation I cut the tabs off the part that fits where the cannons go so it sits flush and added a magnet to the bottom of the statue then put another under the top of the turret so it's held in the center.
For the assault cannon/heavy bolter I just used a pin on the gunner's handle that goes into the gun and holds it in place.
So tonight I will be priming and base coating both of these so the owner can get started painting them.
Oh... and I bought this tonight from a guy that was very motivated to sell it for a great price. Maybe I can get it done this year.