I would not trust a measurement to the string on any single cam bow. I'd use the string over the axle method instead.

There is nothing 'wrong' with having a half inch positive tiller in the top limb. Static tiller, your tiller at brace height, is just a number. A starting point. The real thing you need to worry about... and where many people are missing out on getting the best shooting from their bow... is your DYNAMIC tiller set properly for your grip position and shooting style?

Draw the bow very slowly and pay strict attention to how the bow draws. It helps if you can put your sight pin on an object and see if you can keep it there throughout the draw. Does the bow draw back evenly, top to bottom? Or does the bow feel unbalanced on the draw, with one end trying to pull back sooner than the other? Do you have trouble holding the pin on the object or does the pin pull off, uncontrollably?

If the bow feels like the bottom limb is trying to pull back before the top limb, you need to take back off the bottom limb bolt. If the pin pulls down, you need to back off the bottom limb bolt. If the top limb is trying to pull back before the bottom limb, you need to back off the top limb bolt. If the pin pulls up, you need to back off on the top limb bolt.

You keep adjusting until the bow draws smoothly and evenly, top to bottom, and you can keep that pin on the object throughout the draw.

Your limb bolts probably will not be bottomed out when you're done. One might be, but not the other. Any possible tiny loss in arrow speed is more than offset by having a smoother draw, easier aiming and less noise and recoil.