Fuel Calibration Pitch Attitude

I will be calibrating my fuel quantity indicators and trying to figure out the proper pitch attitude to simulate level flight. What attitude in degrees of pitch should i use? also open to other fuel calibration suggestions for RV-14A with Garmin panel

High speed level flight has the cockpit side rails pretty close to being level.

Don't know if it makes much difference but in a low fuel situation one would probably be flying at best range speed. This would result in a slight nose high attitude. Wouldn't we want the greatest accuracy out of the fuel system in that situation?

Well, actual weight would have an influence as well, so if someone wanted high precision of the calibration, there are a number of things to consider.

Most modern EFIS fuel level indicators have a resolution in increments of single gallons. I have never tested it but my guess would be that the AOA variable induced by weight change and cruise speed would not be any more than 1 gallon.

I personally never rely exclusively on a fuel level indicator for fuel decisions to the point where a 1 gallon difference in indicated value would be important to me.
Ground attitude vs level flight attitude can make quite a bit of difference (particularly in a tail dragger) which is why many of the modern EFIS systems have dual calibration tables and the ground one is used for the displayed values until the EFIS detects the aircraft is in flight.