RE: motor line on the motor box
totaly depends on the desighn of the model. your average floater and sport model will have little effect. A racer it would be the differance between winning and loosing. A pattern ship again could make just that impercise to loose a competition. Otherwise a good trim and mix to counter a negitive effects would be minimal. Usually the onlt reason to go off of center is to make up for the build in thrust angle in a models firewall