That seems reasonable for the hammer/fist. I could just put a fist on, but the hammer looks quite good, so I'll keep that.
Is there much use for a cannon? I could easily block off the magazine and put a heavy MG barrel in there instead. Or, if it's worthwhile, it would be pretty easy to put a magnet in there and be able to switch between cannon and MG.
Then all I've got to do is figure out:
-Should I cut away most of the spikes?
-What should I put in place of the head?
For those who are curious, this is the model.

Mine has a different axe (now trimmed to a hammer) that is usually paired with a fist, but the fist is in use on a different model. I'm making this from leftover parts after I gathered the necessary stuff to make a unit of Lesser Abbysal Golems for Kings of War. They are all going to be made from Khador warjacks and will all have close combat weapons. 6 Warjacks on a movememt gray will be a pretty cool unit, but that the subject for another post.