I just bought a stencil kit for my 68 and had the shop put it on right.
The stencil kit shows you how to line everything up. I was there and helped the guy lay it on right. Make sure you don't center it on the header. The stripe is closer to the front of the header panel. Again, the stencil is designed to minimize *uck ups.
I searched the web, magazines and books and I found that soooo many cars have variations on the bumble bee stripe. In fact, if you have the NPD catalog from a couple months ago, they have a blue Nickey's (I think) Camaro on the cover. Look at the bumble bee stripe. It's centered on the header. That's incorrect. So even the cars worth 40 or 50 grand don't always get it right.
There's a 2" break in the stripe for your engine or RS emblem, although I have seen posts of guys going 2-1/16".