Is there a general rule of thumb to use as to when you should be shifting on the 1-2 or 2-3?

At peak horsepower? 100, 200, 300 rpm later?

Maybe you need a dyno-run sitting in front of you to accurately determine?

Maybe it depends on shift extention and where your peak torque is?

I tried shifting at 6,100, but I noticed things start to go 'flat' up there. Like there is a bit of a lag. I ran 5,900 for a while, but still notice that the motor feels slightly "winded" just before the shift. I bumped them down to 5,700 for the heck of it, and the pull through the gears is much quicker and "cleaner" feeling.

Not sure what to think of this.

 

A little tip...

Your shift points would be optimum if you always dropped back into your torque curve/powerband.

 

I believe the general rule of thumb is 400-500rpm higher than your peak HP...

That being said it is also going to depend on your gearing and converter choice. Before my cam my peak HP was at 5200rpm yet I was still faster in the 1/4 by shiting at 6000 or above so that I stayed in 2nd gear throughout the 1/4. If I shifted earlier and slipped into 3rd my times suffered..