Off-Season training is the best time of year to improve your cycling position.
The legs need a strong core from which to generate power, and muscle recruitment patterns are position-specific (which is why I avoid fitting before races).
Any changes, no matter how beneficial, require a period of adaptation and refinement.
I believe it is better to identify a good position off-season, where light to moderate training loads ensure the development of strong stabilizers and a good foundation for racing.