I'm new to this type of software and blogs, and
have just bought a copy of the Sentient theme.
I have found it possible to set shop to full screen width, in the basic Sentient theme but not in Twenty Twelve style option.
Also I am unable to remove sidebar widgets when viewing selected product for purchase (screen with details and add to cart button), in either the basic Sentient or the Twenty Twelve option.
I find this annoying as it distracts the buyer from buying. I bought Sentient thinking I could easily separate the sales and blog functions.
Sorry no link, as I am creating the site to to sell a book I haven't published yet, and I don't know how long that might take.