I would think that setting the cam timing at the cam sprockets would be much easier and quicker. Plus you need to be able to set up a dial indicator on top of the valves, both on the intake and exhaust side to really know what the timing is at.

Opening the intake cam sooner can increase cylinder filling if during the valve overlap phase the exhaut pipe is doing a good job and because the valve closes sooner it is possible to get higher dynamic compression. And maybe more power everywhere, if you were getting excessive reversion before.

On the exhaust cam the closing point seems to be the most important timing. This is because if the exhaust valve is open too long you will start pumping intake air out the exhaust port.

And unfortunantly most of the above is trial and error work. Although once you get you first dyno run back, the torque and Hp curves will give some idea what direction to go.

Jeff