Are you sure the new bolts are actually thinner? I replaced the control arms on my '05 recently. In my case, the new nuts and bolts have the same thread size as the original, but the socket size of the nuts are smaller, 19mm vs the original 22mm. If you get the bolts from a different source, make sure they not only match the original thread size but also the same or better strength grade. They may be available at Nissan dealers too.