Probably I'm too dump to understand.
I've verified again:
-In linear mod the pieces are positioned on X,Y,Z in respect with the selected piece.
-In curved mod the pieces are positioned accordingly with the curve parameters and the start angle value.
In this last case only the selected piece elevation count for the rest of the pieces.
Anyway, you could post some pictures with the plugin settings, the result problems and eventually a demo file.
Could help to understand the problem and fix it.