Kelvin "4 Wire" Resistance PCB Design Questions
The nature of the Kelvin measurement is that you have a separate current path and measurement path so that no current (except leakage and bias currents) flow through the measurement conductors. 

Thus, the PCB layout (unless the design itself is faulty) is remarkably easy, and I don't expect you'll have any troubles, since series resistance hardly matters. 







simulate this circuit &ndash; Schematic created using CircuitLab

In the above schematic, the exact value of the resistors R1, R2, R3, and R4 hardly matter, provided they are reasonably low. R4 affects the common-mode voltage the instrumentation amp sees, R1 and R2 affect errors due to input offset current (and noise) a bit, but really the PCB layout is not very important until currents and voltage drops start to become significant wrt the common mode range of U1. So you want to keep the voltage drop across R4 reasonably low (not a problem typically unless you use very thin traces and/or very high currents).