In reality, most airliners have the center of pressure behind the center of gravity which provides a nose-down pitch. To counter that, the horizontal stabilizers in the back have an upside-down cross-section, compared to the main wings, which provide a down-force that helps counter-act said nose-down pitch.
I'm not sure you can flip wings upside-down in KSP to replicate this, but you can change the angle of attack of the horizontal stab to encourage down-force. (Angle the leading edge downwards. This will increase the lift of the side facing Kerbin and act as a counter-balance.)
WestAir's post in [FAR]Why my plane has to be like this to fly? was marked as the answer