Shifting a mast just a few inches?

[Smile-n-Nod]

I have read accounts of square-riggers having a mast shifted as little as four inches (full scale) along the keel. Would such a small change have been worth all that trouble? 

[AON]

Do you part your hair on the left, right, or centre... or comb it front to back?

 

I believe it was the same with the rake of the mast... the master or cap'n adjusted it to how they preferred it to be.

[Lieste]

There are two ways a mast is adjusted, position and rake.
A 4" position shift may have limited impact on the trim of the vessel, but it could make the difference between griping or of missing stays or tacking well if right on the margins of 'good' balance. If you move more than 1 mast by these small amounts, then the effect of couple and moment can be enhanced between the masts, and between the masts and the hull.
A 4" change in the rake of the mast between keelson and partners (over say 24') could result in a change in the position of the truck of the mast by nearly 30" in middling ships. (A steeper rake, but less movement per degree of rake for smaller vessels).

Raking the foremast forward increases it's lever, as does raking the mizzen aft. IMO a rake has a greater impact than a shift, but the resulting moment changes more with sail pattern than with less raked, but shifted masting.
Shifts at the partners are also seen, both as shifts of the mast and the rake of the rig.