Keenan, The isolines grid seems to depend on the way the surface is constructed. (eg. The definition seems to fail in certain cases where the surface is derived from a sphere) I’ll need to alter the script and approach (to not use isolines) in order to obtain a regular grid irrespective of the geometry of the surface. However, if you want a non uniform grid, you could try the below file in which the input parameters for the spacing is a range instead of a number.
File: SurfaceSubDivision-1.dyn
I’ve also uploaded the same as a node in the Package Manager (Search for Testing Waters - Surface.DivideByIsolineGrid) 