Hey Kenny,
I haven't done any scientific crono testing and until last night, the carbon strip went in between the tapers, essentially down the middle of the limbs and across the back of the riser. They SEEM faster and more consistent, quieter, and more stable (less chance for limb twist), and definately smoother. I just built one with a .030" carbon strip just below a .030" UL glass so that it is very close to the outside of the back. We'll see how fast it is. I hope the sheer-force between the carbon and the glass doesn't cause it to explode. The layup, back to belly, all 2" wide, 64" recurve was: .030 UL glass, .030 carbon, .110 walnut taper, .090 actionboo taper, .030 bocote parallel. Stack .340 at fattest, .200ish at the tips. We'll see. I pay about $45 for each carbon piece at Binghams. Mike Fedora won't stock it because he feels exposure to the fibers is too dangerous and for the extra 3-4 FPS, he said it's not worth it. I grind mine outdoors with a good respirator so I'm not concerned. I'd say the jury is still out...
Steve