The bain of my early attempts at drawing Space Marines was that I did not know that what the right proportions were for them. I looked at the work of Karl Kopinski (Look at the picture in the front of the 4th edition rulebook of the Ravenguard making planetfall.) I figured them out. Not only did I work out their proportions, but I also figured out what the right proportions for their weapons are. I will porbably refine this later on. All of the Space Marine pics so far posted by me have been done using these proportions. The key is that you base the proportions off of the Space Marine's head, not his helmet.