Post Content with undesirable margins/padding

First of all, thank you for this excellent plugin!

Second, I have not tested it yet fully, but it seems that if I put in the “Post Content” block (widget), having it one column (100%), it has some additional undesirable padding/margin left and right making the content to render in just a narrow middle part of the post/page body.

It looks like this:
http://tinypic.com/r/2yzfxpz/5
the layout setup is here:
http://tinypic.com/r/2zjl355/5

I am experimenting on Twenty Eleven 1.5 template…

Thanks for info
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