Yep, he looks fairly average to my eyes. References are such a good thing. I assume you'll be able to get some front and side elevations in various classic poses (standing and sitting)? The eye can so easily deceive - measure, measure, measure (as a painter I'm forever having to double-check my references).  An incorrectly scaled head or hands can throw things out dramatically. For example, I can't be the only person to have noticed that either M4's head is too small or his hands are massive (possibly both (among other things - I haven't studied him enough). I'd measure in a number of different ways for each body part.
One thing I've noticed a few times with various 3d figures is that body proportions can seem to change based on the pose (i.e. the bending seems to distort a body part or happen around an incorrect pivot such that it looks wrong in the resulting pose). Just thought I'd mention this in case you hadn't considered it.
The type of camera you use in your 3d app can also be problematic. I suspect this is particularly true of Poser. Depending on the camera position and perspective settings, a figure can easily look totally out of proportion whilst in other shots fine. Worth considering when test rendering. I'd tend to measure body parts using orthographic views, and be very careful where you're measuring from and to (not always easy when a body part is bent or obscured).

P.S. The image you just posted is perfectly square on my monitor.

 

PoserPro2014(Sr4), Win7 x64, display units set to inches.

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