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Ellis, it is true that higher offsets stick out less.
Your 17x11 - 56mm wheels would only extend inboard 4mm more than a stock Z06 wheel (18x10.5-58mm). I suspect that the 315 mm tire cross section is the culprit. You would need wheels with less offset or tires with less cross section width to solve your problem - maybe 305mm.
A 1/4 - 3/16 inch hub adapter or spacer may work temporarily till you can wear out the 315s