Are you revving the motor slightly and letting it settle back down to the level it wants to be at, in between readings. You're right about that adjustment screw being a hassle to manipulate. I remove the tank and use a long fuel hose, with the tank sitting up higher than the motor. Also, reverse the manometers to verify your instruments are consistent. Once you get the carbs close to balance, the slightest turn of the adj. screw will result in a change, I have the bike sitting perpendicular (not on the sidestand) to the ground, and have a fan blowing to the front of the motor to maintain a constant run temp. Don't be in a hurry, you'll get better results and they will balance out for you.
