You fail to mention (as do most people posting on here) as to the type of racing are you running , weather its all out, or on a index.
I was fortunet to have a car that ran below the index and never had a tach on the car (cant see it because of vibration). Driver shifts just at the point of feeling peak before going over the nose. I told him "I dont care where you shift at, but shift it at the same point of feel every time and I will adjust the car to the number" I trust the seat of the pants feel of the driver more than a hard to see needle and a shift light bulb that can fail.