Mine was on the car when I bought it so no help here...I would go for rocker panels too if I were you, at least the rear sections as they flare out to the wheel wells because that's where the stones hit. I have one stone chip and that's where it is.....
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Member ZSCCA 2009 Z4 s35i with Dinan Stage II software, Sport and Exec packages, 19" 296 rims , a stubby and mud flaps
'03 Z4 3.0i Sterling Grey (Hers)
'01 Z3 3.0i Sapphire Black, M sport package (Mine)