The Tokina won't hit the mirror regardless of how much you zoom in/out...however, at 11 mm it'll vignette severely (here's a shot I took @ 11 mm with the Tokina 11-16 on my old 1D Mark III):
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I wasn't happy with the vignetting until about 13.5mm, which left the Tokina as basically a prime lens on the 1D3. While it may be a fun toy, I decided that I'd sell the lens and put the $$ towards a 16-35L instead. The 2.5mm won't make a huge difference, but I have a much more versatile and usable lens (and now that I've moved to FF, it makes even more sense to have the 16-35L vs. the Tokina).