From what i've read 205/225 is the best stagger you can go for on the Mk3.
If you put 235's on there, then there's a chance you'll balloon the tyre slightly and you'll get less of a contact area. Which is exactly what you don't want with that beast in the back.
I'm going for some 205/225 17" Toyo T1-R's and see how they last.