Nice. But the muscle expansion doesn't actually correspond to the bone structure. I'm not sure if Marines would still have pectorals to the same extent as regular folk, but given the limitations of the modelling program he seems to be using, it's understandable.
He also leaves out the fact that the ossmoddula doesn't make the bones grow faster by itself, rather it changes the bones structure, using ceramic chemicals in the marine's diet to harden them beyond normal human resistance. In the process he describes, marines would be subject to a great deal of muscle entropy and infection unless constantly supervised and would need to be drip fed their food. Given the constant 'at war' state of all chapters and the relentless training programs this takes up time and personnel that the Chapter should not under any reasonable set of circumstances be able to spare.
I'm also not sure about the muscle proportions used. Marines undergo a great deal of modification to both muscle mass and density, as well as bone composites, so the skeletal structure would be markedly different to that of an unaugmented human, probably in the upper torso and skull, as remarked in the Horus Heresy Books.
More here:
http://uk.games-workshop.com/spacemarines/initiation/1/
Size-wise its fairly good, though for some reason I always thought of SM as taller... For a lot of what they have, they would need to scale up the human frame an awful lot, especially since the standard human genome and bone structure is tailored towards the 6ft line. Beyond that to any great extent is considered abnormal, and markedly dangerous for most people. While taller people can cover more ground they aren't generally faster (especially in the 7' bracket) and their ankles and lower backs would be under considerable stress.
If the joint can't cope with that, the Ossmoddula would need to reinforce that somehow to cope with the additional stresses of the ceramic chemicals, and for the kind of speed and coordination marines are supposed to exhibit outside of their power armour, the amount of testosterone running through the marine's system would be downright imposing in the least.