Pued, I disagree. McGwire was puny compared to his later days. All of the talk about him being on steriods is as legitimate as the talk surrounding Bonds and Sosa.
The thing you can say about Sosa, McGuire and (sorry) Bagwell is that these guys have had their facial features and head size change dramatically over their tenures in MLB. This is a tell tale sign of human growth hormone usage. I think that steroids is a drop in the proverbial bucket.
McGwire was puny because he was still a kid. Sosa started getting big at the age of 28. The same goes for Bonds. McGwire's situation is different because he got bigger as his manhood kicked in. Its also hard to say that Bags is on roids. Some might assume that he has taken substances because of his size. But, if you look at pictures from his early years, he has always had very big forearms, just like now.