Personally, I'm not a big fan of having the rally stripes end at the top of the spoiler either, however, that's ok with me.
Anyways, since I'm planning on having the Dove Tail installed, as far as I can see, I will be going with after market stripes anyways... which of course will be wider and longer than the factory offered too. Hey, GM can't afford to offer 10 different variations either just to satisfy everyones personal tastes... so they simply do what they deem is best and as for the rest... that is what the aftermarket companies are for!
My choices are for the extended left side stripes over the right side factory options. ( Pictured Below )