Thanks for the feedback, gents.
About the size of the Heavy Cannon clips. Yeah, I think they look pretty big too. But, I took as my guide the FloorOb, since that is already in the game and close(ish) to scale. (For most of these, I was simply taking the floor ob, and rotating it and adjusting positioning and some of the lighting effects by varying the pixels).
I tried taking the Auto Cannon clips and scaling them down as they are just a bit small than these Heavy Cannon clips, but I wasn't satisfied with the end results. By reducing them from 4 pixels wide to 3, they looked too small, so I reverted back to the size of the FloorOb.
Cheers, Ivan