I'm not sure if you are looking for a technial critique or a artistic one but since I'm a newbee for poser and 3d work, I can only make artistic sugestions. My first thought is one I often have when seeing pictures of people who do physical labor. He's too clean.  2nd the guy on the left's hat doesn't look like it's touching the head, except maybe on the crown. I'm not familiar with that style of hat (only seen it on the Gordan's fisherman) so maybe it's supposed to be that way.  Putting the chin strap behind the ears might help.  Maybe some hair might too. I don't know.  Also shouldn't there be a zipper of hooks for the straps?
The gut on the right looks like he's in a hazmat suit or a wet suit with boots to me, but again I am not familiar with this style. If that isn't how it's supposed to look, maybe a few folds in the clothing and getting rid of the panty lines might help if you can. Again I'm not that familiar with poser and I've never used 4 so those might not be possible. 
I must say they are better than any thing I can do with it. I could tell that the shirt was a bulky sweater without having to read your discription. The collar and cuffs help I think. And the folds around the elbows.
I hope this helps some otherwise just ignore it. :)

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