Hi Don. Welcome to the GSR!
Let me begin by saying that is a drop-dead gorgeous GS you have there. Congratulations!
In regards to hashmarks placement on the 2010 Grand Sport iterations, it really is just personal preference. Some go with left (driver's side) only, some like 'em on both fenders, and some prefer none at all (SACRILEGE!). Most of us here in the GSR prefer the driver's side only version (ala the '96 GS), as that is more in keeping with the way the stripes were originally used on the early Grand Sport racers. But even then, not all the car's used them and not for every race.
More details and a historical photo in our FAQ section at
http://www.grandspor...y.com/faq.htm#2But hey... it's YOUR car and you can dress it however you please!