Advancing the timing isn't all that straight-forward. It's like compression. If you raise the compression, you'll gain more low end torque, but too much compression, and it will kill your top-end performance. The same is true with timing. Here's a plot of my old 4mm cub motor on racing gas. The lowest HP curve is 4 degrees of timing. The middle curve is 8 degrees, I believe. You can see that significant gains were made everywhere except after the peak. If I had the HP vs Time curve, it's a better view to see how much faster the motor accelerates with respect to time. You can clearly see though, that once the HP peaks, the power just falls off, whereas with the 4 degrees of timing, it held on for longer. The largest curve is 8 degrees with 39mm carbs rather than 36mm, so you can see the effects of going to a larger carb as well.
Almost everything about performance is a trade-off, as you can clearly see in these plots.