superimpose polygons on a grid

Hi all,

is there a way to plot polygons over a grid? It seems that:

spplot(myspgrid, sp.layout(list("sp.polygon",mysppolygon)))

always plots the grid on top of the polygon (as in 
<http://r-spatial.sourceforge.net/gallery/#fig07.R> and contrary to 
lines and points).

Is there any way to change this (for instance to plot a lake area on top 
of a raster DEM)?

cheers
Wouter